diff --git a/src/data/battler-tags.ts b/src/data/battler-tags.ts
index 41a49270c9e..a664ac1e2bf 100644
--- a/src/data/battler-tags.ts
+++ b/src/data/battler-tags.ts
@@ -634,6 +634,32 @@ export class IngrainTag extends TrappedTag {
   }
 }
 
+/**
+ * Octolock traps the target pokemon and reduces its DEF and SPDEF by one stage at the
+ * end of each turn.
+ */
+export class OctolockTag extends TrappedTag {
+  constructor(sourceId: number) {
+    super(BattlerTagType.OCTOLOCK, BattlerTagLapseType.TURN_END, 1, Moves.OCTOLOCK, sourceId);
+  }
+
+  canAdd(pokemon: Pokemon): boolean {
+    const isOctolocked = pokemon.getTag(BattlerTagType.OCTOLOCK);
+    return !isOctolocked;
+  }
+
+  lapse(pokemon: Pokemon, lapseType: BattlerTagLapseType): boolean {
+    const shouldLapse = lapseType !== BattlerTagLapseType.CUSTOM || super.lapse(pokemon, lapseType);
+
+    if (shouldLapse) {
+      pokemon.scene.unshiftPhase(new StatChangePhase(pokemon.scene, pokemon.getBattlerIndex(), true, [BattleStat.DEF, BattleStat.SPDEF], -1));
+      return true;
+    }
+
+    return false;
+  }
+}
+
 export class AquaRingTag extends BattlerTag {
   constructor() {
     super(BattlerTagType.AQUA_RING, BattlerTagLapseType.TURN_END, 1, Moves.AQUA_RING, undefined);
@@ -1662,6 +1688,8 @@ export function getBattlerTag(tagType: BattlerTagType, turnCount: integer, sourc
     return new DestinyBondTag(sourceMove, sourceId);
   case BattlerTagType.ICE_FACE:
     return new IceFaceTag(sourceMove);
+  case BattlerTagType.OCTOLOCK:
+    return new OctolockTag(sourceId);
   case BattlerTagType.NONE:
   default:
     return new BattlerTag(tagType, BattlerTagLapseType.CUSTOM, turnCount, sourceMove, sourceId);
diff --git a/src/data/move.ts b/src/data/move.ts
index 7d798689bea..f244b484e00 100644
--- a/src/data/move.ts
+++ b/src/data/move.ts
@@ -7796,8 +7796,7 @@ export function initMoves() {
       .attr(EatBerryAttr)
       .target(MoveTarget.ALL),
     new StatusMove(Moves.OCTOLOCK, Type.FIGHTING, 100, 15, -1, 0, 8)
-      .attr(AddBattlerTagAttr, BattlerTagType.TRAPPED, false, true, 1)
-      .partial(),
+      .attr(AddBattlerTagAttr, BattlerTagType.OCTOLOCK, false, true, 1),
     new AttackMove(Moves.BOLT_BEAK, Type.ELECTRIC, MoveCategory.PHYSICAL, 85, 100, 10, -1, 0, 8)
       .attr(FirstAttackDoublePowerAttr),
     new AttackMove(Moves.FISHIOUS_REND, Type.WATER, MoveCategory.PHYSICAL, 85, 100, 10, -1, 0, 8)
diff --git a/src/enums/battler-tag-type.ts b/src/enums/battler-tag-type.ts
index 5cdabfe78c2..bb7f7c05b00 100644
--- a/src/enums/battler-tag-type.ts
+++ b/src/enums/battler-tag-type.ts
@@ -13,6 +13,7 @@ export enum BattlerTagType {
   ENCORE = "ENCORE",
   HELPING_HAND = "HELPING_HAND",
   INGRAIN = "INGRAIN",
+  OCTOLOCK = "OCTOLOCK",
   AQUA_RING = "AQUA_RING",
   DROWSY = "DROWSY",
   TRAPPED = "TRAPPED",
diff --git a/src/test/battlerTags/octolock.test.ts b/src/test/battlerTags/octolock.test.ts
new file mode 100644
index 00000000000..4c1c58d4345
--- /dev/null
+++ b/src/test/battlerTags/octolock.test.ts
@@ -0,0 +1,62 @@
+import { describe, expect, it, vi } from "vitest";
+import Pokemon from "#app/field/pokemon.js";
+import BattleScene from "#app/battle-scene.js";
+import { BattlerTag, BattlerTagLapseType, OctolockTag, TrappedTag } from "#app/data/battler-tags.js";
+import { StatChangePhase } from "#app/phases.js";
+import { BattleStat } from "#app/data/battle-stat.js";
+import { BattlerTagType } from "#app/enums/battler-tag-type.js";
+
+jest.mock("#app/battle-scene.js");
+
+describe("BattlerTag - OctolockTag", () => {
+  describe("lapse behavior", () => {
+    it("unshifts a StatChangePhase with expected stat changes", { timeout: 10000 }, async () => {
+      const mockPokemon = {
+        scene: new BattleScene(),
+        getBattlerIndex: () => 0,
+      } as Pokemon;
+
+      const subject = new OctolockTag(1);
+
+      vi.spyOn(mockPokemon.scene, "unshiftPhase").mockImplementation(phase => {
+        expect(phase).toBeInstanceOf(StatChangePhase);
+        expect((phase as StatChangePhase)["levels"]).toEqual(-1);
+        expect((phase as StatChangePhase)["stats"]).toEqual([BattleStat.DEF, BattleStat.SPDEF]);
+      });
+
+      subject.lapse(mockPokemon, BattlerTagLapseType.TURN_END);
+
+      expect(mockPokemon.scene.unshiftPhase).toBeCalledTimes(1);
+    });
+  });
+
+  it ("traps its target (extends TrappedTag)", { timeout: 2000 }, async () => {
+    expect(new OctolockTag(1)).toBeInstanceOf(TrappedTag);
+  });
+
+  it("can be added to pokemon who are not octolocked", { timeout: 2000 }, async => {
+    const mockPokemon = {
+      getTag: vi.fn().mockReturnValue(undefined) as Pokemon["getTag"],
+    } as Pokemon;
+
+    const subject = new OctolockTag(1);
+
+    expect(subject.canAdd(mockPokemon)).toBeTruthy();
+
+    expect(mockPokemon.getTag).toHaveBeenCalledTimes(1);
+    expect(mockPokemon.getTag).toHaveBeenCalledWith(BattlerTagType.OCTOLOCK);
+  });
+
+  it("cannot be added to pokemon who are octolocked", { timeout: 2000 }, async => {
+    const mockPokemon = {
+      getTag: vi.fn().mockReturnValue(new BattlerTag(null, null, null, null)) as Pokemon["getTag"],
+    } as Pokemon;
+
+    const subject = new OctolockTag(1);
+
+    expect(subject.canAdd(mockPokemon)).toBeFalsy();
+
+    expect(mockPokemon.getTag).toHaveBeenCalledTimes(1);
+    expect(mockPokemon.getTag).toHaveBeenCalledWith(BattlerTagType.OCTOLOCK);
+  });
+});
diff --git a/src/test/moves/octolock.test.ts b/src/test/moves/octolock.test.ts
new file mode 100644
index 00000000000..b2798fc15d5
--- /dev/null
+++ b/src/test/moves/octolock.test.ts
@@ -0,0 +1,78 @@
+import {afterEach, beforeAll, beforeEach, describe, expect, it, vi} from "vitest";
+import Phaser from "phaser";
+import GameManager from "#app/test/utils/gameManager";
+import * as overrides from "#app/overrides";
+import { CommandPhase, MoveEndPhase, TurnInitPhase } from "#app/phases";
+import {getMovePosition} from "#app/test/utils/gameManagerUtils";
+import {BattleStat} from "#app/data/battle-stat";
+import { Abilities } from "#enums/abilities";
+import { Moves } from "#enums/moves";
+import { Species } from "#enums/species";
+import { TrappedTag } from "#app/data/battler-tags.js";
+
+describe("Moves - Octolock", () => {
+  describe("integration tests", () => {
+    let phaserGame: Phaser.Game;
+    let game: GameManager;
+
+    beforeAll(() => {
+      phaserGame = new Phaser.Game({
+        type: Phaser.HEADLESS,
+      });
+    });
+
+    afterEach(() => {
+      game.phaseInterceptor.restoreOg();
+    });
+
+    beforeEach(() => {
+      game = new GameManager(phaserGame);
+
+      vi.spyOn(overrides, "SINGLE_BATTLE_OVERRIDE", "get").mockReturnValue(true);
+
+      vi.spyOn(overrides, "OPP_SPECIES_OVERRIDE", "get").mockReturnValue(Species.RATTATA);
+      vi.spyOn(overrides, "OPP_MOVESET_OVERRIDE", "get").mockReturnValue([Moves.SPLASH, Moves.SPLASH, Moves.SPLASH, Moves.SPLASH]);
+      vi.spyOn(overrides, "OPP_ABILITY_OVERRIDE", "get").mockReturnValue(Abilities.NONE);
+
+      vi.spyOn(overrides, "STARTING_LEVEL_OVERRIDE", "get").mockReturnValue(2000);
+      vi.spyOn(overrides, "MOVESET_OVERRIDE", "get").mockReturnValue([Moves.OCTOLOCK, Moves.SPLASH]);
+      vi.spyOn(overrides, "ABILITY_OVERRIDE", "get").mockReturnValue(Abilities.NONE);
+    });
+
+    it("Reduces DEf and SPDEF by 1 each turn", { timeout: 10000 }, async () => {
+      await game.startBattle([Species.GRAPPLOCT]);
+
+      const enemyPokemon = game.scene.getEnemyField();
+
+      // use Octolock and advance to init phase of next turn to check for stat changes
+      game.doAttack(getMovePosition(game.scene, 0, Moves.OCTOLOCK));
+      await game.phaseInterceptor.to(TurnInitPhase);
+
+      expect(enemyPokemon[0].summonData.battleStats[BattleStat.DEF]).toBe(-1);
+      expect(enemyPokemon[0].summonData.battleStats[BattleStat.SPDEF]).toBe(-1);
+
+      // take a second turn to make sure stat changes occur again
+      await game.phaseInterceptor.to(CommandPhase);
+      game.doAttack(getMovePosition(game.scene, 0, Moves.SPLASH));
+
+      await game.phaseInterceptor.to(TurnInitPhase);
+      expect(enemyPokemon[0].summonData.battleStats[BattleStat.DEF]).toBe(-2);
+      expect(enemyPokemon[0].summonData.battleStats[BattleStat.SPDEF]).toBe(-2);
+    });
+
+    it("Traps the target pokemon", { timeout: 10000 }, async () => {
+      await game.startBattle([Species.GRAPPLOCT]);
+
+      const enemyPokemon = game.scene.getEnemyField();
+
+      // before Octolock - enemy should not be trapped
+      expect(enemyPokemon[0].findTag(t => t instanceof TrappedTag)).toBeUndefined();
+
+      game.doAttack(getMovePosition(game.scene, 0, Moves.OCTOLOCK));
+
+      // after Octolock - enemy should be trapped
+      await game.phaseInterceptor.to(MoveEndPhase);
+      expect(enemyPokemon[0].findTag(t => t instanceof TrappedTag)).toBeDefined();
+    });
+  });
+});