diff --git a/include/sta/tacos/statemachine.hpp b/include/sta/tacos/statemachine.hpp
index 9217c1c..07fbdea 100644
--- a/include/sta/tacos/statemachine.hpp
+++ b/include/sta/tacos/statemachine.hpp
@@ -66,6 +66,7 @@
 #include <sta/rtos/event.hpp>
 #include <sta/event.hpp>
 #include <sta/debug/assert.hpp>
+#include <sta/lang.hpp>
 
 #include <functional>
 #include <tuple>
@@ -278,6 +279,18 @@ namespace sta
 			 */
 			std::vector<std::shared_ptr<TacosThread>> threads_[STA_TACOS_NUM_STATES];
 		};
+
+		/**
+		 * @brief Callback that is called when a state transition occurs.
+		 * 
+		 * @param from The state we transitioned from.
+		 * @param to The state we transitioned to.
+		 * @param lockout The lockout time after the transition.
+		 * 
+		 * @ingroup tacos_statemachine
+		 */
+		STA_WEAK
+		void onStateTransition(uint16_t from, uint16_t to, uint32_t lockout){}
 	}  // namespace tacos
 }  // namespace sta
 
diff --git a/src/statemachine.cpp b/src/statemachine.cpp
index 762e48b..2d10a67 100644
--- a/src/statemachine.cpp
+++ b/src/statemachine.cpp
@@ -71,6 +71,9 @@ namespace sta
 				HeapStats_t stats;
 				vPortGetHeapStats(&stats);
 
+				// Execute the user-defined callback.
+				sta::tacos::onStateTransition(transition.from, transition.to, transition.lockout);
+
 				// Start all new tasks and stop all the tasks that aren't supposed to be running.
 				updateThreads();
 			}