diff --git a/soh/soh/ActorExtension/ActorExtension.cpp b/soh/soh/ActorExtension/ActorExtension.cpp
new file mode 100644
index 000000000..df82cd769
--- /dev/null
+++ b/soh/soh/ActorExtension/ActorExtension.cpp
@@ -0,0 +1,78 @@
+#include "ActorExtension.h"
+
+static ActorExtensionId sNextId = 0;
+
+struct ActorExtensionKeyHash {
+    std::size_t operator()(const std::pair<Actor*, ActorExtensionId>& key) const {
+        return std::hash<Actor*>{}(key.first) ^ (std::hash<ActorExtensionId>{}(key.second) << 1);
+    }
+};
+
+static std::unordered_map<ActorExtensionId, size_t> sGlobalSizes;
+static std::unordered_map<s16, std::unordered_map<ActorExtensionId, size_t>> sSizes;
+static std::unordered_map<std::pair<Actor*, ActorExtensionId>, void*, ActorExtensionKeyHash> sData;
+
+void* ActorExtension_Get(Actor* actor, ActorExtensionId id) {
+    if (actor == nullptr) {
+        return nullptr;
+    }
+
+    auto it = sData.find(std::make_pair(actor, id));
+    if (it == sData.end()) {
+        return nullptr;
+    }
+
+    return it->second;
+}
+
+ActorExtensionId ActorExtension_CreateForId(int16_t actorId, size_t size) {
+    ActorExtensionId id = ++sNextId;
+    sSizes[actorId][id] = size;
+    return id;
+}
+
+ActorExtensionId ActorExtension_CreateForAll(size_t size) {
+    ActorExtensionId id = ++sNextId;
+    sGlobalSizes[id] = size;
+    return id;
+}
+
+void ActorExtension_Alloc(Actor* actor, int16_t actorId) {
+    if (actor == nullptr) {
+        return;
+    }
+
+    for (auto& [id, size] : sGlobalSizes) {
+        void* data = malloc(size);
+        memset(data, 0, size);
+        sData[std::make_pair(actor, id)] = data;
+    }
+
+    for (auto& [id, size] : sSizes[actorId]) {
+        void* data = malloc(size);
+        memset(data, 0, size);
+        sData[std::make_pair(actor, id)] = data;
+    }
+}
+
+void ActorExtension_Free(Actor* actor) {
+    if (actor == nullptr) {
+        return;
+    }
+
+    for (auto& [id, size] : sGlobalSizes) {
+        auto it = sData.find(std::make_pair(actor, id));
+        if (it != sData.end()) {
+            free(it->second);
+            sData.erase(it);
+        }
+    }
+
+    for (auto& [id, size] : sSizes[actor->id]) {
+        auto it = sData.find(std::make_pair(actor, id));
+        if (it != sData.end()) {
+            free(it->second);
+            sData.erase(it);
+        }
+    }
+}
\ No newline at end of file
diff --git a/soh/soh/ActorExtension/ActorExtension.h b/soh/soh/ActorExtension/ActorExtension.h
new file mode 100644
index 000000000..01441f76d
--- /dev/null
+++ b/soh/soh/ActorExtension/ActorExtension.h
@@ -0,0 +1,27 @@
+#ifndef ACTOR_EXTENSION_H
+#define ACTOR_EXTENSION_H
+
+#include <libultraship/libultraship.h>
+
+#ifdef __cplusplus
+extern "C" {
+#include <z64actor.h>
+#endif
+
+typedef uint32_t ActorExtensionId;
+
+void* ActorExtension_Get(Actor* actor, ActorExtensionId id);
+
+// These should only ever be called once, before any actors are spawned
+ActorExtensionId ActorExtension_CreateForId(int16_t actorId, size_t size);
+ActorExtensionId ActorExtension_CreateForAll(size_t size);
+
+// Internal, you shouldn't have to touch these
+void ActorExtension_Alloc(Actor* actor, int16_t actorId);
+void ActorExtension_Free(Actor* actor);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif // ACTOR_EXTENSION_H
\ No newline at end of file
diff --git a/soh/soh/ActorExtension/ActorListIndex.cpp b/soh/soh/ActorExtension/ActorListIndex.cpp
new file mode 100644
index 000000000..e46436d85
--- /dev/null
+++ b/soh/soh/ActorExtension/ActorListIndex.cpp
@@ -0,0 +1,32 @@
+#include "ActorListIndex.h"
+#include "soh/ShipInit.hpp"
+#include "soh/Enhancements/game-interactor/GameInteractor.h"
+
+ActorExtensionId actorListIndexActorExt = 0;
+int16_t currentActorListIndex = -1;
+
+static RegisterShipInitFunc initFunc(
+    []() {
+        if (actorListIndexActorExt == 0) {
+            actorListIndexActorExt = ActorExtension_CreateForAll(sizeof(int16_t));
+        }
+    },
+    {});
+
+int16_t GetActorListIndex(Actor* actor) {
+    int16_t* listIndex = (int16_t*)ActorExtension_Get(actor, actorListIndexActorExt);
+    if (listIndex == nullptr) {
+        return -1;
+    }
+    return *listIndex;
+}
+
+void SetActorListIndex(Actor* actor, int16_t index) {
+    int16_t* listIndex = (int16_t*)ActorExtension_Get(actor, actorListIndexActorExt);
+
+    if (listIndex == nullptr) {
+        assert(false);
+    } else {
+        *listIndex = index;
+    }
+}
\ No newline at end of file
diff --git a/soh/soh/ActorExtension/ActorListIndex.h b/soh/soh/ActorExtension/ActorListIndex.h
new file mode 100644
index 000000000..397cc7e37
--- /dev/null
+++ b/soh/soh/ActorExtension/ActorListIndex.h
@@ -0,0 +1,22 @@
+#ifndef ACTOR_LIST_INDEX_H
+#define ACTOR_LIST_INDEX_H
+
+#include <libultraship/libultraship.h>
+#include <soh/ActorExtension/ActorExtension.h>
+
+#ifdef __cplusplus
+extern "C" {
+#include "z64actor.h"
+#endif
+
+extern ActorExtensionId actorListIndexActorExt;
+extern int16_t currentActorListIndex;
+
+int16_t GetActorListIndex(Actor* actor);
+void SetActorListIndex(Actor* actor, int16_t index);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif // ACTOR_LIST_INDEX_H
\ No newline at end of file
diff --git a/soh/soh/Enhancements/debugger/actorViewer.cpp b/soh/soh/Enhancements/debugger/actorViewer.cpp
index 515da6491..883fb795c 100644
--- a/soh/soh/Enhancements/debugger/actorViewer.cpp
+++ b/soh/soh/Enhancements/debugger/actorViewer.cpp
@@ -26,6 +26,7 @@ extern PlayState* gPlayState;
 
 #include "textures/icon_item_static/icon_item_static.h"
 #include "textures/icon_item_24_static/icon_item_24_static.h"
+#include <soh/ActorExtension/ActorListIndex.h>
 }
 
 #define DEKUNUTS_FLOWER 10
@@ -925,6 +926,7 @@ void ActorViewerWindow::DrawElement() {
                     ImGui::Text("Category: %s", acMapping[display->category]);
                     ImGui::Text("ID: %d", display->id);
                     ImGui::Text("Parameters: %d", display->params);
+                    ImGui::Text("Actor List Index: %d", GetActorListIndex(display));
                 },
                 "Selected Actor");
             ImGui::SameLine();
diff --git a/soh/src/code/z_actor.c b/soh/src/code/z_actor.c
index 3ca67ad3b..56f65516c 100644
--- a/soh/src/code/z_actor.c
+++ b/soh/src/code/z_actor.c
@@ -1,4 +1,5 @@
 #include "global.h"
+#include "soh/ActorExtension/ActorExtension.h"
 #include "vt.h"
 
 #include "overlays/actors/ovl_Arms_Hook/z_arms_hook.h"
@@ -80,6 +81,7 @@
 #include "textures/place_title_cards/g_pn_56.h"
 #include "textures/place_title_cards/g_pn_57.h"
 #endif
+#include <soh/ActorExtension/ActorListIndex.h>
 
 static CollisionPoly* sCurCeilingPoly;
 static s32 sCurCeilingBgId;
@@ -2574,8 +2576,14 @@ void Actor_UpdateAll(PlayState* play, ActorContext* actorCtx) {
     if (play->numSetupActors != 0) {
         actorEntry = &play->setupActorList[0];
         for (i = 0; i < play->numSetupActors; i++) {
+            // #region SOH [ActorExtension] ActorListIndex tracking
+            currentActorListIndex = i;
+            // #endregion
             Actor_SpawnEntry(&play->actorCtx, actorEntry++, play);
         }
+        // #region SOH [ActorExtension] ActorListIndex tracking
+        currentActorListIndex = -1;
+        // #endregion
         play->numSetupActors = 0;
         GameInteractor_ExecuteOnSceneSpawnActors();
     }
@@ -3352,6 +3360,12 @@ Actor* Actor_Spawn(ActorContext* actorCtx, PlayState* play, s16 actorId, f32 pos
         return NULL;
     }
 
+    // #region SOH [ActorExtension]
+    ActorExtension_Alloc(actor, dbEntry->id);
+    SetActorListIndex(actor, currentActorListIndex);
+    currentActorListIndex = -1;
+    // #endregion
+
     assert(dbEntry->numLoaded < 255);
 
     dbEntry->numLoaded++;
@@ -3494,6 +3508,10 @@ Actor* Actor_Delete(ActorContext* actorCtx, Actor* actor, PlayState* play) {
 
     newHead = Actor_RemoveFromCategory(play, actorCtx, actor);
 
+    // #region SOH [ActorExtension]
+    ActorExtension_Free(actor);
+    // #endregion
+
     ZELDA_ARENA_FREE_DEBUG(actor);
 
     dbEntry->numLoaded--;