diff --git a/.gitmodules b/.gitmodules
new file mode 100644
index 0000000..4c994e1
--- /dev/null
+++ b/.gitmodules
@@ -0,0 +1,3 @@
+[submodule "ext/BehaviorTree.ROS2"]
+	path = ext/BehaviorTree.ROS2
+	url = https://github.com/BehaviorTree/BehaviorTree.ROS2.git
diff --git a/ext/BehaviorTree.ROS2 b/ext/BehaviorTree.ROS2
new file mode 160000
index 0000000..6c6aa07
--- /dev/null
+++ b/ext/BehaviorTree.ROS2
@@ -0,0 +1 @@
+Subproject commit 6c6aa078ee7bc52fec98984bed4964556abf5beb