diff --git a/AngleAxis.cpp b/AngleAxis.cpp
index 49379ef..2ed8321 100644
--- a/AngleAxis.cpp
+++ b/AngleAxis.cpp
@@ -22,6 +22,15 @@ AngleAxis<T>::AngleAxis(float angle, Vector3 axis) {
   this->axis = Direction<T>(axis);
 }
 
+template <typename T>
+AngleAxis<T>::AngleAxis(Quaternion q) {
+  float angle;
+  Vector3 axis;
+  q.ToAngleAxis(&angle, &axis);
+  this->angle = AngleOf<T>(angle);
+  this->axis = Direction<T>(axis);
+}
+
 template <typename T>
 Quaternion AngleAxis<T>::ToQuaternion() {
   Vector3 axisVector = this->axis.ToVector3();
diff --git a/AngleAxis.h b/AngleAxis.h
index 14e2f3d..fbd0ec2 100644
--- a/AngleAxis.h
+++ b/AngleAxis.h
@@ -20,6 +20,7 @@ class AngleAxis {
 
   AngleAxis();
   AngleAxis(AngleOf<T> angle, Direction<T> axis);
+  AngleAxis(Quaternion q);
   AngleAxis(float angle, Vector3 axis);
 
   Quaternion ToQuaternion();