diff --git a/apriltag/src/main/native/include/frc/apriltag/AprilTagDetection.h b/apriltag/src/main/native/include/frc/apriltag/AprilTagDetection.h
index 5225f2176b..babcbd8309 100644
--- a/apriltag/src/main/native/include/frc/apriltag/AprilTagDetection.h
+++ b/apriltag/src/main/native/include/frc/apriltag/AprilTagDetection.h
@@ -9,10 +9,9 @@
 #include <span>
 #include <string_view>
 
+#include <Eigen/Core>
 #include <wpi/SymbolExports.h>
 
-#include "frc/EigenCore.h"
-
 namespace frc {
 
 /**
diff --git a/wpilibc/src/main/native/cpp/simulation/DifferentialDrivetrainSim.cpp b/wpilibc/src/main/native/cpp/simulation/DifferentialDrivetrainSim.cpp
index b6c95dc0ab..8c27cdf15b 100644
--- a/wpilibc/src/main/native/cpp/simulation/DifferentialDrivetrainSim.cpp
+++ b/wpilibc/src/main/native/cpp/simulation/DifferentialDrivetrainSim.cpp
@@ -41,7 +41,8 @@ DifferentialDrivetrainSim::DifferentialDrivetrainSim(
               driveMotor, mass, wheelRadius, trackWidth / 2.0, J, gearing),
           trackWidth, driveMotor, gearing, wheelRadius, measurementStdDevs) {}
 
-Vectord<2> DifferentialDrivetrainSim::ClampInput(const Vectord<2>& u) {
+Eigen::Vector2d DifferentialDrivetrainSim::ClampInput(
+    const Eigen::Vector2d& u) {
   return frc::DesaturateInputVector<2>(u,
                                        frc::RobotController::GetInputVoltage());
 }
@@ -128,7 +129,7 @@ void DifferentialDrivetrainSim::SetPose(const frc::Pose2d& pose) {
 }
 
 Vectord<7> DifferentialDrivetrainSim::Dynamics(const Vectord<7>& x,
-                                               const Vectord<2>& u) {
+                                               const Eigen::Vector2d& u) {
   // Because G² can be factored out of A, we can divide by the old ratio
   // squared and multiply by the new ratio squared to get a new drivetrain
   // model.
diff --git a/wpilibc/src/main/native/include/frc/simulation/DifferentialDrivetrainSim.h b/wpilibc/src/main/native/include/frc/simulation/DifferentialDrivetrainSim.h
index 812943a2c9..78310d78c7 100644
--- a/wpilibc/src/main/native/include/frc/simulation/DifferentialDrivetrainSim.h
+++ b/wpilibc/src/main/native/include/frc/simulation/DifferentialDrivetrainSim.h
@@ -80,7 +80,7 @@ class DifferentialDrivetrainSim {
    * @param u The input vector.
    * @return The normalized input.
    */
-  Vectord<2> ClampInput(const Vectord<2>& u);
+  Eigen::Vector2d ClampInput(const Eigen::Vector2d& u);
 
   /**
    * Sets the applied voltage to the drivetrain. Note that positive voltage must
@@ -187,7 +187,7 @@ class DifferentialDrivetrainSim {
    */
   void SetPose(const frc::Pose2d& pose);
 
-  Vectord<7> Dynamics(const Vectord<7>& x, const Vectord<2>& u);
+  Vectord<7> Dynamics(const Vectord<7>& x, const Eigen::Vector2d& u);
 
   class State {
    public:
@@ -325,7 +325,7 @@ class DifferentialDrivetrainSim {
   double m_currentGearing;
 
   Vectord<7> m_x;
-  Vectord<2> m_u;
+  Eigen::Vector2d m_u;
   Vectord<7> m_y;
   std::array<double, 7> m_measurementStdDevs;
 };
diff --git a/wpimath/src/main/native/cpp/StateSpaceUtil.cpp b/wpimath/src/main/native/cpp/StateSpaceUtil.cpp
index 4e606189b4..758d2e772a 100644
--- a/wpimath/src/main/native/cpp/StateSpaceUtil.cpp
+++ b/wpimath/src/main/native/cpp/StateSpaceUtil.cpp
@@ -6,16 +6,16 @@
 
 namespace frc {
 
-Vectord<3> PoseTo3dVector(const Pose2d& pose) {
-  return Vectord<3>{pose.Translation().X().value(),
-                    pose.Translation().Y().value(),
-                    pose.Rotation().Radians().value()};
+Eigen::Vector3d PoseTo3dVector(const Pose2d& pose) {
+  return Eigen::Vector3d{pose.Translation().X().value(),
+                         pose.Translation().Y().value(),
+                         pose.Rotation().Radians().value()};
 }
 
-Vectord<4> PoseTo4dVector(const Pose2d& pose) {
-  return Vectord<4>{pose.Translation().X().value(),
-                    pose.Translation().Y().value(), pose.Rotation().Cos(),
-                    pose.Rotation().Sin()};
+Eigen::Vector4d PoseTo4dVector(const Pose2d& pose) {
+  return Eigen::Vector4d{pose.Translation().X().value(),
+                         pose.Translation().Y().value(), pose.Rotation().Cos(),
+                         pose.Rotation().Sin()};
 }
 
 template <>
@@ -34,9 +34,9 @@ bool IsStabilizable<Eigen::Dynamic, Eigen::Dynamic>(const Eigen::MatrixXd& A,
   return detail::IsStabilizableImpl<Eigen::Dynamic, Eigen::Dynamic>(A, B);
 }
 
-Vectord<3> PoseToVector(const Pose2d& pose) {
-  return Vectord<3>{pose.X().value(), pose.Y().value(),
-                    pose.Rotation().Radians().value()};
+Eigen::Vector3d PoseToVector(const Pose2d& pose) {
+  return Eigen::Vector3d{pose.X().value(), pose.Y().value(),
+                         pose.Rotation().Radians().value()};
 }
 
 }  // namespace frc
diff --git a/wpimath/src/main/native/cpp/controller/DifferentialDriveFeedforward.cpp b/wpimath/src/main/native/cpp/controller/DifferentialDriveFeedforward.cpp
index e1b2732642..257d7e1efc 100644
--- a/wpimath/src/main/native/cpp/controller/DifferentialDriveFeedforward.cpp
+++ b/wpimath/src/main/native/cpp/controller/DifferentialDriveFeedforward.cpp
@@ -4,7 +4,8 @@
 
 #include "frc/controller/DifferentialDriveFeedforward.h"
 
-#include "frc/EigenCore.h"
+#include <Eigen/Core>
+
 #include "frc/controller/LinearPlantInversionFeedforward.h"
 #include "frc/system/plant/LinearSystemId.h"
 
@@ -30,8 +31,8 @@ DifferentialDriveWheelVoltages DifferentialDriveFeedforward::Calculate(
     units::meters_per_second_t nextRightVelocity, units::second_t dt) {
   frc::LinearPlantInversionFeedforward<2, 2> feedforward{m_plant, dt};
 
-  frc::Vectord<2> r{currentLeftVelocity, currentRightVelocity};
-  frc::Vectord<2> nextR{nextLeftVelocity, nextRightVelocity};
+  Eigen::Vector2d r{currentLeftVelocity, currentRightVelocity};
+  Eigen::Vector2d nextR{nextLeftVelocity, nextRightVelocity};
   auto u = feedforward.Calculate(r, nextR);
   return {units::volt_t{u(0)}, units::volt_t{u(1)}};
 }
diff --git a/wpimath/src/main/native/cpp/geometry/CoordinateSystem.cpp b/wpimath/src/main/native/cpp/geometry/CoordinateSystem.cpp
index 400a5e5617..2a8c9db154 100644
--- a/wpimath/src/main/native/cpp/geometry/CoordinateSystem.cpp
+++ b/wpimath/src/main/native/cpp/geometry/CoordinateSystem.cpp
@@ -8,6 +8,7 @@
 #include <stdexcept>
 #include <utility>
 
+#include <Eigen/Core>
 #include <Eigen/QR>
 
 using namespace frc;
@@ -18,7 +19,7 @@ CoordinateSystem::CoordinateSystem(const CoordinateAxis& positiveX,
   // Construct a change of basis matrix from the source coordinate system to the
   // NWU coordinate system. Each column vector in the change of basis matrix is
   // one of the old basis vectors mapped to its representation in the new basis.
-  Matrixd<3, 3> R;
+  Eigen::Matrix3d R;
   R.block<3, 1>(0, 0) = positiveX.m_axis;
   R.block<3, 1>(0, 1) = positiveY.m_axis;
   R.block<3, 1>(0, 2) = positiveZ.m_axis;
diff --git a/wpimath/src/main/native/cpp/geometry/Pose3d.cpp b/wpimath/src/main/native/cpp/geometry/Pose3d.cpp
index 845ea7d0e4..f479b0d705 100644
--- a/wpimath/src/main/native/cpp/geometry/Pose3d.cpp
+++ b/wpimath/src/main/native/cpp/geometry/Pose3d.cpp
@@ -6,6 +6,7 @@
 
 #include <cmath>
 
+#include <Eigen/Core>
 #include <wpi/json.h>
 
 using namespace frc;
@@ -21,14 +22,14 @@ namespace {
  * @param rotation The rotation vector.
  * @return The rotation vector as a 3x3 rotation matrix.
  */
-Matrixd<3, 3> RotationVectorToMatrix(const Vectord<3>& rotation) {
+Eigen::Matrix3d RotationVectorToMatrix(const Eigen::Vector3d& rotation) {
   // Given a rotation vector <a, b, c>,
   //         [ 0 -c  b]
   // Omega = [ c  0 -a]
   //         [-b  a  0]
-  return Matrixd<3, 3>{{0.0, -rotation(2), rotation(1)},
-                       {rotation(2), 0.0, -rotation(0)},
-                       {-rotation(1), rotation(0), 0.0}};
+  return Eigen::Matrix3d{{0.0, -rotation(2), rotation(1)},
+                         {rotation(2), 0.0, -rotation(0)},
+                         {-rotation(1), rotation(0), 0.0}};
 }
 }  // namespace
 
diff --git a/wpimath/src/main/native/cpp/geometry/Rotation3d.cpp b/wpimath/src/main/native/cpp/geometry/Rotation3d.cpp
index a898d0d577..d1f18464a1 100644
--- a/wpimath/src/main/native/cpp/geometry/Rotation3d.cpp
+++ b/wpimath/src/main/native/cpp/geometry/Rotation3d.cpp
@@ -41,23 +41,23 @@ Rotation3d::Rotation3d(units::radian_t roll, units::radian_t pitch,
 Rotation3d::Rotation3d(const Eigen::Vector3d& rvec)
     : Rotation3d{rvec, units::radian_t{rvec.norm()}} {}
 
-Rotation3d::Rotation3d(const Vectord<3>& axis, units::radian_t angle) {
+Rotation3d::Rotation3d(const Eigen::Vector3d& axis, units::radian_t angle) {
   double norm = axis.norm();
   if (norm == 0.0) {
     return;
   }
 
   // https://en.wikipedia.org/wiki/Conversion_between_quaternions_and_Euler_angles#Definition
-  Vectord<3> v = axis / norm * units::math::sin(angle / 2.0);
+  Eigen::Vector3d v = axis / norm * units::math::sin(angle / 2.0);
   m_q = Quaternion{units::math::cos(angle / 2.0), v(0), v(1), v(2)};
 }
 
-Rotation3d::Rotation3d(const Matrixd<3, 3>& rotationMatrix) {
+Rotation3d::Rotation3d(const Eigen::Matrix3d& rotationMatrix) {
   const auto& R = rotationMatrix;
 
   // Require that the rotation matrix is special orthogonal. This is true if the
   // matrix is orthogonal (RRᵀ = I) and normalized (determinant is 1).
-  if ((R * R.transpose() - Matrixd<3, 3>::Identity()).norm() > 1e-9) {
+  if ((R * R.transpose() - Eigen::Matrix3d::Identity()).norm() > 1e-9) {
     std::string msg =
         fmt::format("Rotation matrix isn't orthogonal\n\nR =\n{}\n", R);
 
@@ -112,7 +112,8 @@ Rotation3d::Rotation3d(const Matrixd<3, 3>& rotationMatrix) {
   m_q = Quaternion{w, x, y, z};
 }
 
-Rotation3d::Rotation3d(const Vectord<3>& initial, const Vectord<3>& final) {
+Rotation3d::Rotation3d(const Eigen::Vector3d& initial,
+                       const Eigen::Vector3d& final) {
   double dot = initial.dot(final);
   double normProduct = initial.norm() * final.norm();
   double dotNorm = dot / normProduct;
@@ -230,7 +231,7 @@ units::radian_t Rotation3d::Z() const {
   }
 }
 
-Vectord<3> Rotation3d::Axis() const {
+Eigen::Vector3d Rotation3d::Axis() const {
   double norm = std::hypot(m_q.X(), m_q.Y(), m_q.Z());
   if (norm == 0.0) {
     return {0.0, 0.0, 0.0};
diff --git a/wpimath/src/main/native/cpp/kinematics/MecanumDriveKinematics.cpp b/wpimath/src/main/native/cpp/kinematics/MecanumDriveKinematics.cpp
index c7618d545b..c21a7b2034 100644
--- a/wpimath/src/main/native/cpp/kinematics/MecanumDriveKinematics.cpp
+++ b/wpimath/src/main/native/cpp/kinematics/MecanumDriveKinematics.cpp
@@ -25,7 +25,7 @@ MecanumDriveWheelSpeeds MecanumDriveKinematics::ToWheelSpeeds(
                                       chassisSpeeds.vy.value(),
                                       chassisSpeeds.omega.value()};
 
-  Vectord<4> wheelsVector = m_inverseKinematics * chassisSpeedsVector;
+  Eigen::Vector4d wheelsVector = m_inverseKinematics * chassisSpeedsVector;
 
   MecanumDriveWheelSpeeds wheelSpeeds;
   wheelSpeeds.frontLeft = units::meters_per_second_t{wheelsVector(0)};
@@ -37,7 +37,7 @@ MecanumDriveWheelSpeeds MecanumDriveKinematics::ToWheelSpeeds(
 
 ChassisSpeeds MecanumDriveKinematics::ToChassisSpeeds(
     const MecanumDriveWheelSpeeds& wheelSpeeds) const {
-  Vectord<4> wheelSpeedsVector{
+  Eigen::Vector4d wheelSpeedsVector{
       wheelSpeeds.frontLeft.value(), wheelSpeeds.frontRight.value(),
       wheelSpeeds.rearLeft.value(), wheelSpeeds.rearRight.value()};
 
@@ -52,7 +52,7 @@ ChassisSpeeds MecanumDriveKinematics::ToChassisSpeeds(
 Twist2d MecanumDriveKinematics::ToTwist2d(
     const MecanumDriveWheelPositions& start,
     const MecanumDriveWheelPositions& end) const {
-  Vectord<4> wheelDeltasVector{
+  Eigen::Vector4d wheelDeltasVector{
       end.frontLeft.value() - start.frontLeft.value(),
       end.frontRight.value() - start.frontRight.value(),
       end.rearLeft.value() - start.rearLeft.value(),
@@ -66,7 +66,7 @@ Twist2d MecanumDriveKinematics::ToTwist2d(
 
 Twist2d MecanumDriveKinematics::ToTwist2d(
     const MecanumDriveWheelPositions& wheelDeltas) const {
-  Vectord<4> wheelDeltasVector{
+  Eigen::Vector4d wheelDeltasVector{
       wheelDeltas.frontLeft.value(), wheelDeltas.frontRight.value(),
       wheelDeltas.rearLeft.value(), wheelDeltas.rearRight.value()};
 
diff --git a/wpimath/src/main/native/include/frc/StateSpaceUtil.h b/wpimath/src/main/native/include/frc/StateSpaceUtil.h
index aefc2f12f7..8c2ac65481 100644
--- a/wpimath/src/main/native/include/frc/StateSpaceUtil.h
+++ b/wpimath/src/main/native/include/frc/StateSpaceUtil.h
@@ -226,7 +226,7 @@ Vectord<N> MakeWhiteNoiseVector(const std::array<double, N>& stdDevs) {
  * @return The vector.
  */
 WPILIB_DLLEXPORT
-Vectord<3> PoseTo3dVector(const Pose2d& pose);
+Eigen::Vector3d PoseTo3dVector(const Pose2d& pose);
 
 /**
  * Converts a Pose2d into a vector of [x, y, std::cos(theta), std::sin(theta)].
@@ -236,7 +236,7 @@ Vectord<3> PoseTo3dVector(const Pose2d& pose);
  * @return The vector.
  */
 WPILIB_DLLEXPORT
-Vectord<4> PoseTo4dVector(const Pose2d& pose);
+Eigen::Vector4d PoseTo4dVector(const Pose2d& pose);
 
 /**
  * Returns true if (A, B) is a stabilizable pair.
@@ -301,7 +301,7 @@ WPILIB_DLLEXPORT bool IsStabilizable<Eigen::Dynamic, Eigen::Dynamic>(
  * @return The vector.
  */
 WPILIB_DLLEXPORT
-Vectord<3> PoseToVector(const Pose2d& pose);
+Eigen::Vector3d PoseToVector(const Pose2d& pose);
 
 /**
  * Clamps input vector between system's minimum and maximum allowable input.
diff --git a/wpimath/src/main/native/include/frc/estimator/MecanumDrivePoseEstimator.h b/wpimath/src/main/native/include/frc/estimator/MecanumDrivePoseEstimator.h
index 52794fb844..d748164f47 100644
--- a/wpimath/src/main/native/include/frc/estimator/MecanumDrivePoseEstimator.h
+++ b/wpimath/src/main/native/include/frc/estimator/MecanumDrivePoseEstimator.h
@@ -9,7 +9,6 @@
 #include <wpi/SymbolExports.h>
 #include <wpi/array.h>
 
-#include "frc/EigenCore.h"
 #include "frc/estimator/PoseEstimator.h"
 #include "frc/geometry/Pose2d.h"
 #include "frc/geometry/Rotation2d.h"
diff --git a/wpimath/src/main/native/include/frc/estimator/PoseEstimator.h b/wpimath/src/main/native/include/frc/estimator/PoseEstimator.h
index 542ab2e315..eb437a40f7 100644
--- a/wpimath/src/main/native/include/frc/estimator/PoseEstimator.h
+++ b/wpimath/src/main/native/include/frc/estimator/PoseEstimator.h
@@ -4,10 +4,10 @@
 
 #pragma once
 
+#include <Eigen/Core>
 #include <wpi/SymbolExports.h>
 #include <wpi/array.h>
 
-#include "frc/EigenCore.h"
 #include "frc/geometry/Pose2d.h"
 #include "frc/geometry/Rotation2d.h"
 #include "frc/interpolation/TimeInterpolatableBuffer.h"
diff --git a/wpimath/src/main/native/include/frc/estimator/PoseEstimator.inc b/wpimath/src/main/native/include/frc/estimator/PoseEstimator.inc
index 1bd6e3d0a0..79d71bcc56 100644
--- a/wpimath/src/main/native/include/frc/estimator/PoseEstimator.inc
+++ b/wpimath/src/main/native/include/frc/estimator/PoseEstimator.inc
@@ -81,9 +81,9 @@ void PoseEstimator<WheelSpeeds, WheelPositions>::AddVisionMeasurement(
   // Step 3: We should not trust the twist entirely, so instead we scale this
   // twist by a Kalman gain matrix representing how much we trust vision
   // measurements compared to our current pose.
-  Vectord<3> k_times_twist =
+  Eigen::Vector3d k_times_twist =
       m_visionK *
-      Vectord<3>{twist.dx.value(), twist.dy.value(), twist.dtheta.value()};
+      Eigen::Vector3d{twist.dx.value(), twist.dy.value(), twist.dtheta.value()};
 
   // Step 4: Convert back to Twist2d
   Twist2d scaledTwist{units::meter_t{k_times_twist(0)},
diff --git a/wpimath/src/main/native/include/frc/geometry/CoordinateAxis.h b/wpimath/src/main/native/include/frc/geometry/CoordinateAxis.h
index 58b966ab07..2b471b7d5d 100644
--- a/wpimath/src/main/native/include/frc/geometry/CoordinateAxis.h
+++ b/wpimath/src/main/native/include/frc/geometry/CoordinateAxis.h
@@ -4,9 +4,9 @@
 
 #pragma once
 
+#include <Eigen/Core>
 #include <wpi/SymbolExports.h>
 
-#include "frc/EigenCore.h"
 #include "frc/geometry/Pose3d.h"
 #include "frc/geometry/Rotation3d.h"
 
@@ -67,7 +67,7 @@ class WPILIB_DLLEXPORT CoordinateAxis {
  private:
   friend class CoordinateSystem;
 
-  Vectord<3> m_axis;
+  Eigen::Vector3d m_axis;
 };
 
 }  // namespace frc
diff --git a/wpimath/src/main/native/include/frc/geometry/CoordinateSystem.h b/wpimath/src/main/native/include/frc/geometry/CoordinateSystem.h
index 232455ff86..f5e71f2b28 100644
--- a/wpimath/src/main/native/include/frc/geometry/CoordinateSystem.h
+++ b/wpimath/src/main/native/include/frc/geometry/CoordinateSystem.h
@@ -6,7 +6,6 @@
 
 #include <wpi/SymbolExports.h>
 
-#include "frc/EigenCore.h"
 #include "frc/geometry/CoordinateAxis.h"
 #include "frc/geometry/Pose3d.h"
 #include "frc/geometry/Rotation3d.h"
diff --git a/wpimath/src/main/native/include/frc/geometry/Quaternion.h b/wpimath/src/main/native/include/frc/geometry/Quaternion.h
index 44b7991cdf..a41e5b80bf 100644
--- a/wpimath/src/main/native/include/frc/geometry/Quaternion.h
+++ b/wpimath/src/main/native/include/frc/geometry/Quaternion.h
@@ -4,10 +4,9 @@
 
 #pragma once
 
+#include <Eigen/Core>
 #include <wpi/SymbolExports.h>
 
-#include "frc/EigenCore.h"
-
 namespace wpi {
 class json;
 }  // namespace wpi
diff --git a/wpimath/src/main/native/include/frc/geometry/Rotation3d.h b/wpimath/src/main/native/include/frc/geometry/Rotation3d.h
index e49787073a..887f01a970 100644
--- a/wpimath/src/main/native/include/frc/geometry/Rotation3d.h
+++ b/wpimath/src/main/native/include/frc/geometry/Rotation3d.h
@@ -4,9 +4,9 @@
 
 #pragma once
 
+#include <Eigen/Core>
 #include <wpi/SymbolExports.h>
 
-#include "frc/EigenCore.h"
 #include "frc/geometry/Quaternion.h"
 #include "frc/geometry/Rotation2d.h"
 #include "units/angle.h"
@@ -57,7 +57,7 @@ class WPILIB_DLLEXPORT Rotation3d {
    * @param axis The rotation axis.
    * @param angle The rotation around the axis.
    */
-  Rotation3d(const Vectord<3>& axis, units::radian_t angle);
+  Rotation3d(const Eigen::Vector3d& axis, units::radian_t angle);
 
   /**
    * Constructs a Rotation3d with the given rotation vector representation. This
@@ -86,7 +86,7 @@ class WPILIB_DLLEXPORT Rotation3d {
    * @param initial The initial vector.
    * @param final The final vector.
    */
-  Rotation3d(const Vectord<3>& initial, const Vectord<3>& final);
+  Rotation3d(const Eigen::Vector3d& initial, const Eigen::Vector3d& final);
 
   /**
    * Adds two rotations together.
@@ -173,7 +173,7 @@ class WPILIB_DLLEXPORT Rotation3d {
   /**
    * Returns the axis in the axis-angle representation of this rotation.
    */
-  Vectord<3> Axis() const;
+  Eigen::Vector3d Axis() const;
 
   /**
    * Returns the angle in the axis-angle representation of this rotation.
diff --git a/wpimath/src/main/native/include/frc/spline/CubicHermiteSpline.h b/wpimath/src/main/native/include/frc/spline/CubicHermiteSpline.h
index 0636707958..1d6aaeb60e 100644
--- a/wpimath/src/main/native/include/frc/spline/CubicHermiteSpline.h
+++ b/wpimath/src/main/native/include/frc/spline/CubicHermiteSpline.h
@@ -49,7 +49,7 @@ class WPILIB_DLLEXPORT CubicHermiteSpline : public Spline<3> {
    * Returns the hermite basis matrix for cubic hermite spline interpolation.
    * @return The hermite basis matrix for cubic hermite spline interpolation.
    */
-  static Matrixd<4, 4> MakeHermiteBasis() {
+  static Eigen::Matrix4d MakeHermiteBasis() {
     // Given P(i), P'(i), P(i+1), P'(i+1), the control vectors, we want to find
     // the coefficients of the spline P(t) = a₃t³ + a₂t² + a₁t + a₀.
     //
@@ -71,10 +71,10 @@ class WPILIB_DLLEXPORT CubicHermiteSpline : public Spline<3> {
     // [a₁] = [ 0  1  0  0][P(i+1) ]
     // [a₀] = [ 1  0  0  0][P'(i+1)]
 
-    static const Matrixd<4, 4> basis{{+2.0, +1.0, -2.0, +1.0},
-                                     {-3.0, -2.0, +3.0, -1.0},
-                                     {+0.0, +1.0, +0.0, +0.0},
-                                     {+1.0, +0.0, +0.0, +0.0}};
+    static const Eigen::Matrix4d basis{{+2.0, +1.0, -2.0, +1.0},
+                                       {-3.0, -2.0, +3.0, -1.0},
+                                       {+0.0, +1.0, +0.0, +0.0},
+                                       {+1.0, +0.0, +0.0, +0.0}};
     return basis;
   }
 
diff --git a/wpimath/src/main/native/include/frc/system/NumericalIntegration.h b/wpimath/src/main/native/include/frc/system/NumericalIntegration.h
index 4f7ba319ea..98b6cc3044 100644
--- a/wpimath/src/main/native/include/frc/system/NumericalIntegration.h
+++ b/wpimath/src/main/native/include/frc/system/NumericalIntegration.h
@@ -4,12 +4,9 @@
 
 #pragma once
 
-#include <frc/StateSpaceUtil.h>
-
 #include <algorithm>
 #include <array>
-
-#include <Eigen/Core>
+#include <cmath>
 
 #include "units/time.h"
 
diff --git a/wpimath/src/test/native/cpp/EigenTest.cpp b/wpimath/src/test/native/cpp/EigenTest.cpp
index 20f708778a..74c8577aaa 100644
--- a/wpimath/src/test/native/cpp/EigenTest.cpp
+++ b/wpimath/src/test/native/cpp/EigenTest.cpp
@@ -30,17 +30,17 @@ TEST(EigenTest, Multiplication) {
 }
 
 TEST(EigenTest, Transpose) {
-  frc::Vectord<3> vec{1, 2, 3};
+  Eigen::Vector3d vec{1, 2, 3};
 
   const auto transpose = vec.transpose();
 
-  Eigen::RowVector<double, 3> expectedTranspose{1, 2, 3};
+  Eigen::RowVector3d expectedTranspose{1, 2, 3};
 
   EXPECT_TRUE(expectedTranspose.isApprox(transpose));
 }
 
 TEST(EigenTest, Inverse) {
-  frc::Matrixd<3, 3> mat{{1.0, 3.0, 2.0}, {5.0, 2.0, 1.5}, {0.0, 1.3, 2.5}};
+  Eigen::Matrix3d mat{{1.0, 3.0, 2.0}, {5.0, 2.0, 1.5}, {0.0, 1.3, 2.5}};
 
   const auto inverse = mat.inverse();
   const auto identity = Eigen::MatrixXd::Identity(3, 3);
diff --git a/wpimath/src/test/native/cpp/controller/DifferentialDriveFeedforwardTest.cpp b/wpimath/src/test/native/cpp/controller/DifferentialDriveFeedforwardTest.cpp
index 0ae246bb4e..5428d843ca 100644
--- a/wpimath/src/test/native/cpp/controller/DifferentialDriveFeedforwardTest.cpp
+++ b/wpimath/src/test/native/cpp/controller/DifferentialDriveFeedforwardTest.cpp
@@ -4,9 +4,9 @@
 
 #include <cmath>
 
+#include <Eigen/Core>
 #include <gtest/gtest.h>
 
-#include "frc/EigenCore.h"
 #include "frc/controller/DifferentialDriveFeedforward.h"
 #include "frc/controller/LinearPlantInversionFeedforward.h"
 #include "frc/system/plant/LinearSystemId.h"
@@ -38,9 +38,9 @@ TEST(DifferentialDriveFeedforwardTest, CalculateWithTrackwidth) {
           auto [left, right] = differentialDriveFeedforward.Calculate(
               currentLeftVelocity, nextLeftVelocity, currentRightVelocity,
               nextRightVelocity, dt);
-          frc::Matrixd<2, 1> nextX = plant.CalculateX(
-              frc::Vectord<2>{currentLeftVelocity, currentRightVelocity},
-              frc::Vectord<2>{left, right}, dt);
+          Eigen::Vector2d nextX = plant.CalculateX(
+              Eigen::Vector2d{currentLeftVelocity, currentRightVelocity},
+              Eigen::Vector2d{left, right}, dt);
           EXPECT_NEAR(nextX(0), nextLeftVelocity.value(), 1e-6);
           EXPECT_NEAR(nextX(1), nextRightVelocity.value(), 1e-6);
         }
@@ -72,9 +72,9 @@ TEST(DifferentialDriveFeedforwardTest, CalculateWithoutTrackwidth) {
           auto [left, right] = differentialDriveFeedforward.Calculate(
               currentLeftVelocity, nextLeftVelocity, currentRightVelocity,
               nextRightVelocity, dt);
-          frc::Matrixd<2, 1> nextX = plant.CalculateX(
-              frc::Vectord<2>{currentLeftVelocity, currentRightVelocity},
-              frc::Vectord<2>{left, right}, dt);
+          Eigen::Vector2d nextX = plant.CalculateX(
+              Eigen::Vector2d{currentLeftVelocity, currentRightVelocity},
+              Eigen::Vector2d{left, right}, dt);
           EXPECT_NEAR(nextX(0), nextLeftVelocity.value(), 1e-6);
           EXPECT_NEAR(nextX(1), nextRightVelocity.value(), 1e-6);
         }
diff --git a/wpimath/src/test/native/cpp/geometry/Rotation3dTest.cpp b/wpimath/src/test/native/cpp/geometry/Rotation3dTest.cpp
index aa2ea1176f..01b37e5b10 100644
--- a/wpimath/src/test/native/cpp/geometry/Rotation3dTest.cpp
+++ b/wpimath/src/test/native/cpp/geometry/Rotation3dTest.cpp
@@ -5,10 +5,10 @@
 #include <cmath>
 #include <numbers>
 
+#include <Eigen/Core>
 #include <gtest/gtest.h>
 #include <wpi/MathExtras.h>
 
-#include "frc/EigenCore.h"
 #include "frc/geometry/Rotation3d.h"
 
 using namespace frc;
@@ -73,25 +73,25 @@ TEST(Rotation3dTest, InitAxisAngleAndRollPitchYaw) {
 
 TEST(Rotation3dTest, InitRotationMatrix) {
   // No rotation
-  const Matrixd<3, 3> R1 = Matrixd<3, 3>::Identity();
+  const Eigen::Matrix3d R1 = Eigen::Matrix3d::Identity();
   const Rotation3d rot1{R1};
   EXPECT_EQ(Rotation3d{}, rot1);
 
   // 90 degree CCW rotation around z-axis
-  Matrixd<3, 3> R2;
-  R2.block<3, 1>(0, 0) = Vectord<3>{0.0, 1.0, 0.0};
-  R2.block<3, 1>(0, 1) = Vectord<3>{-1.0, 0.0, 0.0};
-  R2.block<3, 1>(0, 2) = Vectord<3>{0.0, 0.0, 1.0};
+  Eigen::Matrix3d R2;
+  R2.block<3, 1>(0, 0) = Eigen::Vector3d{0.0, 1.0, 0.0};
+  R2.block<3, 1>(0, 1) = Eigen::Vector3d{-1.0, 0.0, 0.0};
+  R2.block<3, 1>(0, 2) = Eigen::Vector3d{0.0, 0.0, 1.0};
   const Rotation3d rot2{R2};
   const Rotation3d expected2{0_deg, 0_deg, 90_deg};
   EXPECT_EQ(expected2, rot2);
 
   // Matrix that isn't orthogonal
-  const Matrixd<3, 3> R3{{1.0, 0.0, 0.0}, {1.0, 0.0, 0.0}, {1.0, 0.0, 0.0}};
+  const Eigen::Matrix3d R3{{1.0, 0.0, 0.0}, {1.0, 0.0, 0.0}, {1.0, 0.0, 0.0}};
   EXPECT_THROW(Rotation3d{R3}, std::domain_error);
 
   // Matrix that's orthogonal but not special orthogonal
-  const Matrixd<3, 3> R4 = Matrixd<3, 3>::Identity() * 2.0;
+  const Eigen::Matrix3d R4 = Eigen::Matrix3d::Identity() * 2.0;
   EXPECT_THROW(Rotation3d{R4}, std::domain_error);
 }
 
diff --git a/wpimath/src/test/native/cpp/system/NumericalIntegrationTest.cpp b/wpimath/src/test/native/cpp/system/NumericalIntegrationTest.cpp
index 45acb77829..1c73195ca7 100644
--- a/wpimath/src/test/native/cpp/system/NumericalIntegrationTest.cpp
+++ b/wpimath/src/test/native/cpp/system/NumericalIntegrationTest.cpp
@@ -6,6 +6,7 @@
 
 #include <gtest/gtest.h>
 
+#include "frc/EigenCore.h"
 #include "frc/system/NumericalIntegration.h"
 
 // Tests that integrating dx/dt = e^x works.
diff --git a/wpimath/src/test/native/cpp/system/RungeKuttaTimeVaryingTest.cpp b/wpimath/src/test/native/cpp/system/RungeKuttaTimeVaryingTest.cpp
index d88908c339..e502e95f28 100644
--- a/wpimath/src/test/native/cpp/system/RungeKuttaTimeVaryingTest.cpp
+++ b/wpimath/src/test/native/cpp/system/RungeKuttaTimeVaryingTest.cpp
@@ -6,6 +6,7 @@
 
 #include <gtest/gtest.h>
 
+#include "frc/EigenCore.h"
 #include "frc/system/RungeKuttaTimeVarying.h"
 
 namespace {
diff --git a/wpimath/src/test/native/include/frc/system/RungeKuttaTimeVarying.h b/wpimath/src/test/native/include/frc/system/RungeKuttaTimeVarying.h
index 5e7b165708..6273532b65 100644
--- a/wpimath/src/test/native/include/frc/system/RungeKuttaTimeVarying.h
+++ b/wpimath/src/test/native/include/frc/system/RungeKuttaTimeVarying.h
@@ -6,7 +6,6 @@
 
 #include <array>
 
-#include "frc/EigenCore.h"
 #include "units/time.h"
 
 namespace frc {