diff --git a/wpilibc/src/main/native/include/frc/ADXL345_I2C.h b/wpilibc/src/main/native/include/frc/ADXL345_I2C.h
index c9973270d2..6b6b76c64a 100644
--- a/wpilibc/src/main/native/include/frc/ADXL345_I2C.h
+++ b/wpilibc/src/main/native/include/frc/ADXL345_I2C.h
@@ -19,6 +19,10 @@ namespace frc {
  * This class allows access to a Analog Devices ADXL345 3-axis accelerometer on
  * an I2C bus. This class assumes the default (not alternate) sensor address of
  * 0x1D (7-bit address).
+ *
+ * The Onboard I2C port is subject to system lockups. See <a
+ * href="https://docs.wpilib.org/en/stable/docs/yearly-overview/known-issues.html#onboard-i2c-causing-system-lockups">
+ * WPILib Known Issues</a> page for details.
  */
 class ADXL345_I2C : public Accelerometer,
                     public nt::NTSendable,
diff --git a/wpilibc/src/main/native/include/frc/I2C.h b/wpilibc/src/main/native/include/frc/I2C.h
index d874a46cdf..9489fcfb3e 100644
--- a/wpilibc/src/main/native/include/frc/I2C.h
+++ b/wpilibc/src/main/native/include/frc/I2C.h
@@ -15,6 +15,10 @@ namespace frc {
  *
  * This class is intended to be used by sensor (and other I2C device) drivers.
  * It probably should not be used directly.
+ *
+ * The Onboard I2C port is subject to system lockups. See <a
+ * href="https://docs.wpilib.org/en/stable/docs/yearly-overview/known-issues.html#onboard-i2c-causing-system-lockups">
+ * WPILib Known Issues</a> page for details.
  */
 class I2C {
  public:
diff --git a/wpilibj/src/main/java/edu/wpi/first/wpilibj/ADXL345_I2C.java b/wpilibj/src/main/java/edu/wpi/first/wpilibj/ADXL345_I2C.java
index 29d3930efc..03c81d5524 100644
--- a/wpilibj/src/main/java/edu/wpi/first/wpilibj/ADXL345_I2C.java
+++ b/wpilibj/src/main/java/edu/wpi/first/wpilibj/ADXL345_I2C.java
@@ -18,7 +18,13 @@ import edu.wpi.first.wpilibj.interfaces.Accelerometer;
 import java.nio.ByteBuffer;
 import java.nio.ByteOrder;
 
-/** ADXL345 I2C Accelerometer. */
+/**
+ * ADXL345 I2C Accelerometer.
+ *
+ * <p>The Onboard I2C port is subject to system lockups. See <a
+ * href="https://docs.wpilib.org/en/stable/docs/yearly-overview/known-issues.html#onboard-i2c-causing-system-lockups">
+ * WPILib Known Issues</a> page for details.
+ */
 @SuppressWarnings({"TypeName", "PMD.UnusedPrivateField"})
 public class ADXL345_I2C implements Accelerometer, NTSendable, AutoCloseable {
   private static final byte kAddress = 0x1D;
diff --git a/wpilibj/src/main/java/edu/wpi/first/wpilibj/I2C.java b/wpilibj/src/main/java/edu/wpi/first/wpilibj/I2C.java
index 03a00cc3a2..f4bce1132a 100644
--- a/wpilibj/src/main/java/edu/wpi/first/wpilibj/I2C.java
+++ b/wpilibj/src/main/java/edu/wpi/first/wpilibj/I2C.java
@@ -17,6 +17,10 @@ import java.nio.ByteBuffer;
  *
  * <p>This class is intended to be used by sensor (and other I2C device) drivers. It probably should
  * not be used directly.
+ *
+ * <p>The Onboard I2C port is subject to system lockups. See <a
+ * href="https://docs.wpilib.org/en/stable/docs/yearly-overview/known-issues.html#onboard-i2c-causing-system-lockups">
+ * WPILib Known Issues</a> page for details.
  */
 public class I2C implements AutoCloseable {
   public enum Port {