diff --git a/app/assets/stylesheets/pages/admin/_mission_submissions.scss b/app/assets/stylesheets/pages/admin/_mission_submissions.scss
index 798ce131d..76a5cdc84 100644
--- a/app/assets/stylesheets/pages/admin/_mission_submissions.scss
+++ b/app/assets/stylesheets/pages/admin/_mission_submissions.scss
@@ -830,6 +830,26 @@
     resize: vertical;
   }
 
+  &__detach {
+    display: flex;
+    flex-direction: column;
+    gap: var(--space-xxs);
+  }
+
+  &__detach-option {
+    display: flex;
+    align-items: center;
+    gap: var(--space-xs);
+    cursor: pointer;
+    font-size: 0.95rem;
+  }
+
+  &__detach-hint {
+    font-size: 0.85rem;
+    color: var(--muted);
+    margin: 0;
+  }
+
   &__payout-note {
     font-size: 0.9rem;
     color: var(--color-brand-yellow);
diff --git a/app/controllers/admin/missions/submissions_controller.rb b/app/controllers/admin/missions/submissions_controller.rb
index 8c49ba06f..0ea137958 100644
--- a/app/controllers/admin/missions/submissions_controller.rb
+++ b/app/controllers/admin/missions/submissions_controller.rb
@@ -93,6 +93,10 @@ def update
                       alert: "This submission can't be #{new_status} right now." and return
         end
 
+        detach_requested = new_status == "rejected" &&
+                           ActiveModel::Type::Boolean.new.cast(params.dig(:mission_submission, :detach_project))
+        detached = false
+
         Mission::Submission.transaction do
           if new_status == "approved"
             @submission.update!(reviewed_by: current_user, reviewed_at: Time.current, rejection_message: nil)
@@ -102,14 +106,16 @@ def update
           else
             @submission.update!(reviewed_by: current_user, reviewed_at: Time.current, rejection_message: feedback)
             @submission.reject!
+            detached = detach_submission_project! if detach_requested
           end
         end
 
         notify_builder(new_status)
 
         reviewed = Mission::Submission.reviewed_today(current_user, mission: @mission)
+        verdict = detached ? "Rejected and detached the project" : new_status.titleize
         redirect_to next_admin_mission_submissions_path(mission_slug),
-                    notice: "#{new_status.titleize}. That's #{reviewed} reviewed today."
+                    notice: "#{verdict}. That's #{reviewed} reviewed today."
       end
 
       def next
@@ -281,6 +287,20 @@ def reverse_fixed_stardust_if_granted
         )
       end
 
+      # Detaches the submission's project from the mission it was rejected on,
+      # but only while that mission is still the project's current one — so we
+      # never yank a mission the builder has since swapped to. Returns whether
+      # a detach actually happened. The MissionAttachment change is versioned
+      # by PaperTrail (whodunnit set in the admin controller chain).
+      def detach_submission_project!
+        project = @submission.ship_event&.post&.project
+        return false unless project
+        return false unless project.current_mission == @submission.mission
+
+        project.detach_mission!
+        true
+      end
+
       def notify_builder(status)
         builder = @submission.ship_event&.post&.user
         return unless builder
diff --git a/app/views/admin/missions/submissions/_form.html.erb b/app/views/admin/missions/submissions/_form.html.erb
index 210c3bc95..6c037a1d6 100644
--- a/app/views/admin/missions/submissions/_form.html.erb
+++ b/app/views/admin/missions/submissions/_form.html.erb
@@ -21,6 +21,17 @@
           placeholder: "Required for rejections. Optional for approvals." %>
   </label>
 
+  <div class="mission-review__detach">
+    <label class="mission-review__detach-option">
+      <%= check_box_tag "mission_submission[detach_project]", "1", false %>
+      Also detach this project from the mission
+    </label>
+    <p class="mission-review__detach-hint">
+      Only applies when rejecting. Frees the project from <%= mission.name %> so
+      the builder can pick a different mission.
+    </p>
+  </div>
+
   <% grants = [] %>
   <% if submission.payout_path == "static_prize" %>
     <% grants << "#{mission.fixed_stardust_payout} stardust" if mission.fixed_stardust_payout&.positive? %>
diff --git a/test/controllers/admin/missions/submissions_controller_test.rb b/test/controllers/admin/missions/submissions_controller_test.rb
index 8525b38f2..1028ee7b9 100644
--- a/test/controllers/admin/missions/submissions_controller_test.rb
+++ b/test/controllers/admin/missions/submissions_controller_test.rb
@@ -44,6 +44,41 @@ class Admin::Missions::SubmissionsControllerTest < ActionDispatch::IntegrationTe
     assert @submission.reload.pending?
   end
 
+  test "plain reject leaves the project attached to the mission" do
+    sign_in @reviewer
+    Mission::Submission.atomic_claim!(@submission.id, @reviewer)
+
+    patch admin_mission_submission_path(@mission.slug, @submission),
+          params: { mission_submission: { status: "rejected", feedback: "Needs work" } }
+
+    assert_redirected_to next_admin_mission_submissions_path(@mission.slug)
+    assert @submission.reload.rejected?
+    assert_equal @mission, @project.reload.current_mission
+  end
+
+  test "reject and detach frees the project from the mission" do
+    sign_in @reviewer
+    Mission::Submission.atomic_claim!(@submission.id, @reviewer)
+
+    patch admin_mission_submission_path(@mission.slug, @submission),
+          params: { mission_submission: { status: "rejected", feedback: "Needs work", detach_project: "1" } }
+
+    assert_redirected_to next_admin_mission_submissions_path(@mission.slug)
+    assert @submission.reload.rejected?
+    assert_nil @project.reload.current_mission
+  end
+
+  test "detach flag is ignored when approving" do
+    sign_in @reviewer
+    Mission::Submission.atomic_claim!(@submission.id, @reviewer)
+
+    patch admin_mission_submission_path(@mission.slug, @submission),
+          params: { mission_submission: { status: "approved", detach_project: "1" } }
+
+    assert @submission.reload.approved?
+    assert_equal @mission, @project.reload.current_mission
+  end
+
   test "claims are exclusive while fresh and stealable when expired" do
     other = User.create!(email: "other-#{SecureRandom.hex(4)}@example.test",
                          display_name: "other-#{SecureRandom.hex(4)}",