diff --git a/src/xrt/auxiliary/math/m_api.h b/src/xrt/auxiliary/math/m_api.h
index 923b5fac7..0506e02e9 100644
--- a/src/xrt/auxiliary/math/m_api.h
+++ b/src/xrt/auxiliary/math/m_api.h
@@ -318,6 +318,15 @@ math_matrix_2x2_multiply(const struct xrt_matrix_2x2 *left,
                          const struct xrt_matrix_2x2 *right,
                          struct xrt_matrix_2x2 *result_out);
 
+/*!
+ * Initialize a 3x3 matrix to the identity matrix
+ *
+ * @see xrt_matrix_3x3
+ * @ingroup aux_math
+ */
+void
+math_matrix_3x3_identity(struct xrt_matrix_3x3 *mat);
+
 void
 math_matrix_3x3_transform_vec3(const struct xrt_matrix_3x3 *left,
                                const struct xrt_vec3 *right,
diff --git a/src/xrt/auxiliary/math/m_base.cpp b/src/xrt/auxiliary/math/m_base.cpp
index c5dd83ddb..4c04d4bfd 100644
--- a/src/xrt/auxiliary/math/m_base.cpp
+++ b/src/xrt/auxiliary/math/m_base.cpp
@@ -364,6 +364,12 @@ math_matrix_2x2_multiply(const struct xrt_matrix_2x2 *left,
 	*result_out = result;
 }
 
+extern "C" void
+math_matrix_3x3_identity(struct xrt_matrix_3x3 *mat)
+{
+	mat->v[0] = mat->v[4] = mat->v[8] = 1.0;
+}
+
 extern "C" void
 math_matrix_3x3_transform_vec3(const struct xrt_matrix_3x3 *left,
                                const struct xrt_vec3 *right,