diff --git a/common/locales/en/api-v3.json b/common/locales/en/api-v3.json
index 40382590a6..87c63de581 100644
--- a/common/locales/en/api-v3.json
+++ b/common/locales/en/api-v3.json
@@ -75,6 +75,9 @@
   "questLevelTooHigh": "You must be Level <%= level %> to begin this quest.",
   "questAlreadyUnderway": "Your party is already on a quest. Try again when the current quest has ended.",
   "questAlreadyAccepted": "You already accepted the quest invitation.",
+  "noActiveQuestToLeave": "No active quest to leave",
+  "questLeaderCannotLeaveQuest": "Quest leader cannot leave quest",
+  "notPartOfQuest": "You are not part of the quest",
   "noActiveQuestToAbort": "There is no active quest to abort.",
   "onlyLeaderAbortQuest": "Only the group or quest leader can abort a quest.",
   "questAlreadyRejected": "You already rejected the quest invitation.",
diff --git a/test/api/v3/integration/quests/POST-groups_groupid_quests_leave.test.js b/test/api/v3/integration/quests/POST-groups_groupid_quests_leave.test.js
new file mode 100644
index 0000000000..8b34278c08
--- /dev/null
+++ b/test/api/v3/integration/quests/POST-groups_groupid_quests_leave.test.js
@@ -0,0 +1,124 @@
+import {
+  createAndPopulateGroup,
+  translate as t,
+  generateUser,
+} from '../../../../helpers/api-v3-integration.helper';
+import { v4 as generateUUID } from 'uuid';
+
+describe('POST /groups/:groupId/quests/leave', () => {
+  let questingGroup;
+  let partyMembers;
+  let user;
+  let leader;
+
+  const PET_QUEST = 'whale';
+
+  beforeEach(async () => {
+    let { group, groupLeader, members } = await createAndPopulateGroup({
+      groupDetails: { type: 'party', privacy: 'private' },
+      members: 2,
+    });
+
+    questingGroup = group;
+    leader = groupLeader;
+    partyMembers = members;
+
+    await leader.update({
+      [`items.quests.${PET_QUEST}`]: 1,
+    });
+    user = await generateUser();
+  });
+
+  context('failure conditions', () => {
+    it('returns an error when group is not found', async () => {
+      await expect(partyMembers[0].post(`/groups/${generateUUID()}/quests/leave`))
+        .to.eventually.be.rejected.and.eql({
+          code: 404,
+          error: 'NotFound',
+          message: t('groupNotFound'),
+        });
+    });
+
+    it('returns an error for a group in which user is not a member', async () => {
+      await expect(user.post(`/groups/${questingGroup._id}/quests/leave`))
+      .to.eventually.be.rejected.and.eql({
+        code: 404,
+        error: 'NotFound',
+        message: t('groupNotFound'),
+      });
+    });
+
+    it('returns an error when group is a guild', async () => {
+      let { group: guild, groupLeader: guildLeader } = await createAndPopulateGroup({
+        groupDetails: { type: 'guild', privacy: 'private' },
+      });
+
+      await expect(guildLeader.post(`/groups/${guild._id}/quests/leave`))
+      .to.eventually.be.rejected.and.eql({
+        code: 401,
+        error: 'NotAuthorized',
+        message: t('guildQuestsNotSupported'),
+      });
+    });
+
+    it('returns an error when quest is not active', async () => {
+      await expect(partyMembers[0].post(`/groups/${questingGroup._id}/quests/leave`))
+        .to.eventually.be.rejected.and.eql({
+          code: 404,
+          error: 'NotFound',
+          message: t('noActiveQuestToLeave'),
+        });
+    });
+
+    it('returns an error when quest leader attempts to leave', async () => {
+      await leader.post(`/groups/${questingGroup._id}/quests/invite/${PET_QUEST}`);
+      await partyMembers[0].post(`/groups/${questingGroup._id}/quests/accept`);
+      await partyMembers[1].post(`/groups/${questingGroup._id}/quests/accept`);
+
+      await expect(leader.post(`/groups/${questingGroup._id}/quests/leave`))
+        .to.eventually.be.rejected.and.eql({
+          code: 401,
+          error: 'NotAuthorized',
+          message: t('questLeaderCannotLeaveQuest'),
+        });
+    });
+
+    it('returns an error when non quest member attempts to leave', async () => {
+      await leader.post(`/groups/${questingGroup._id}/quests/invite/${PET_QUEST}`);
+      await partyMembers[0].post(`/groups/${questingGroup._id}/quests/accept`);
+      await partyMembers[1].post(`/groups/${questingGroup._id}/quests/reject`);
+
+      await expect(partyMembers[0].post(`/groups/${questingGroup._id}/quests/leave`))
+      .to.eventually.be.rejected.and.eql({
+        code: 401,
+        error: 'NotAuthorized',
+        message: t('notPartOfQuest'),
+      });
+    });
+  });
+
+  it('leaves a quest', async () => {
+    await leader.post(`/groups/${questingGroup._id}/quests/invite/${PET_QUEST}`);
+    await partyMembers[0].post(`/groups/${questingGroup._id}/quests/accept`);
+    await partyMembers[1].post(`/groups/${questingGroup._id}/quests/accept`);
+
+    let leaveResult = await partyMembers[0].post(`/groups/${questingGroup._id}/quests/leave`);
+    await Promise.all([
+      partyMembers[0].sync(),
+      questingGroup.sync(),
+    ]);
+
+    expect(partyMembers[0].party.quest).to.eql({
+      key: null,
+      progress: {
+        up: 0,
+        down: 0,
+        collect: {},
+      },
+      completed: null,
+      RSVPNeeded: false,
+    });
+    expect(questingGroup.quest).to.deep.equal(leaveResult);
+    expect(questingGroup.quest.members[partyMembers[0]._id]).to.be.false;
+  });
+});
diff --git a/website/src/controllers/api-v3/quests.js b/website/src/controllers/api-v3/quests.js
index d5464f3720..bf25b81396 100644
--- a/website/src/controllers/api-v3/quests.js
+++ b/website/src/controllers/api-v3/quests.js
@@ -341,4 +341,50 @@ api.abortQuest = {
   },
 };
 
+/**
+ * @api {post} /groups/:groupId/quests/leave Leaves the active quest
+ * @apiVersion 3.0.0
+ * @apiName LeaveQuest
+ * @apiGroup Group
+ *
+ * @apiParam {string} groupId The group _id (or 'party')
+ *
+ * @apiSuccess {Object} quest Quest Object
+ */
+api.leaveQuest = {
+  method: 'POST',
+  url: '/groups/:groupId/quests/leave',
+  middlewares: [authWithHeaders(), cron],
+  async handler (req, res) {
+    let user = res.locals.user;
+    let groupId = req.params.groupId;
+
+    req.checkParams('groupId', res.t('groupIdRequired')).notEmpty();
+
+    let validationErrors = req.validationErrors();
+    if (validationErrors) throw validationErrors;
+
+    let group = await Group.getGroup({user, groupId, fields: 'type quest'});
+
+    if (!group) throw new NotFound(res.t('groupNotFound'));
+    if (group.type !== 'party') throw new NotAuthorized(res.t('guildQuestsNotSupported'));
+    if (!group.quest.active) throw new NotFound(res.t('noActiveQuestToLeave'));
+    if (group.quest.leader === user._id) throw new NotAuthorized(res.t('questLeaderCannotLeaveQuest'));
+    if (!group.quest.members[user._id]) throw new NotAuthorized(res.t('notPartOfQuest'));
+
+    group.quest.members[user._id] = false;
+    group.markModified('quest.members');
+
+    user.party.quest = Group.cleanQuestProgress();
+    user.markModified('party.quest');
+
+    let [savedGroup] = await Q.all([
+      group.save(),
+      user.save(),
+    ]);
+
+    res.respond(200, savedGroup.quest);
+  },
+};
+
 export default api;