diff --git a/docs/content/releases/os_upgrading/2.56.md b/docs/content/releases/os_upgrading/2.56.md
new file mode 100644
index 0000000000..59d3171af4
--- /dev/null
+++ b/docs/content/releases/os_upgrading/2.56.md
@@ -0,0 +1,27 @@
+---
+title: 'Upgrading to DefectDojo Version 2.56.x'
+toc_hide: true
+weight: -20260215
+description: Deprecation of Questionnaire API Endpoints
+---
+
+## Deprecation: Questionnaire API Endpoints
+
+The following Questionnaire API endpoints are being deprecated and will be removed in DefectDojo 2.59.0 on June 1st, 2026:
+
+- `/api/v2/questionnaire_answered_questionnaires/`
+- `/api/v2/questionnaire_answers/`
+- `/api/v2/questionnaire_engagement_questionnaires/`
+- `/api/v2/questionnaire_general_questionnaires/`
+- `/api/v2/questionnaire_questions`
+
+### Required Actions
+
+Support for these endpoints will be fully removed in DefectDojo 2.59.0 (scheduled for June 1st, 2026). After this date, any requests to these endpoints will return a 404 Not Found error.
+
+### Timeline
+
+- **DefectDojo 2.56.x onwards**: Endpoints are deprecated with deprecation headers
+- **DefectDojo 2.59.0 (June 1st, 2026)**: Endpoints will be removed entirely
+
+For more information, check the [Release Notes](https://github.com/DefectDojo/django-DefectDojo/releases/tag/2.56.0).
diff --git a/docs/content/releases/os_upgrading/2.59.md b/docs/content/releases/os_upgrading/2.59.md
new file mode 100644
index 0000000000..d5bb68b3ab
--- /dev/null
+++ b/docs/content/releases/os_upgrading/2.59.md
@@ -0,0 +1,22 @@
+---
+title: 'Upgrading to DefectDojo Version 2.59.x'
+toc_hide: true
+weight: -20260602
+description: Removal of Questionnaire API Endpoints
+---
+
+## Removal: Questionnaire API Endpoints
+
+As announced in DefectDojo 2.56.0, the following Questionnaire API endpoints have been removed:
+
+- `/api/v2/questionnaire_answered_questionnaires/`
+- `/api/v2/questionnaire_answers/`
+- `/api/v2/questionnaire_engagement_questionnaires/`
+- `/api/v2/questionnaire_general_questionnaires/`
+- `/api/v2/questionnaire_questions`
+
+### Required Actions
+
+Any requests to these endpoints will now return a 404 Not Found error.
+
+For more information, check the [Release Notes](https://github.com/DefectDojo/django-DefectDojo/releases/tag/2.59.0).
diff --git a/dojo/api_v2/views.py b/dojo/api_v2/views.py
index 15ba41e3d0..e8790df5b4 100644
--- a/dojo/api_v2/views.py
+++ b/dojo/api_v2/views.py
@@ -242,6 +242,19 @@ class PrefetchDojoModelViewSet(
     pass
 
 
+class DeprecationNoticeMixin:
+
+    deprecated: bool | None = None
+    end_of_life_date: datetime | None = None
+
+    def finalize_response(self, request, response, *args, **kwargs):
+        if self.deprecated is not None:
+            response["X-Deprecated"] = self.deprecated
+        if self.end_of_life_date is not None:
+            response["X-End-Of-Life-Date"] = self.end_of_life_date.isoformat()
+        return super().finalize_response(request, response, *args, **kwargs)
+
+
 # Authorization: authenticated users
 class RoleViewSet(viewsets.ReadOnlyModelViewSet):
     serializer_class = serializers.RoleSerializer
@@ -3171,7 +3184,10 @@ def get_queryset(self):
 class QuestionnaireQuestionViewSet(
     viewsets.ReadOnlyModelViewSet,
     dojo_mixins.QuestionSubClassFieldsMixin,
+    DeprecationNoticeMixin,
 ):
+    deprecated = True
+    end_of_life_date = datetime(2026, 6, 1)
     serializer_class = serializers.QuestionnaireQuestionSerializer
     queryset = Question.objects.none()
     filter_backends = (DjangoFilterBackend,)
@@ -3183,11 +3199,28 @@ class QuestionnaireQuestionViewSet(
     def get_queryset(self):
         return Question.objects.all().order_by("id")
 
+    @extend_schema(
+        deprecated=True,
+        description="This endpoint is deprecated and will be removed on 2026-06-01.",
+    )
+    def list(self, request, *args, **kwargs):
+        return super().list(request, *args, **kwargs)
+
+    @extend_schema(
+        deprecated=True,
+        description="This endpoint is deprecated and will be removed on 2026-06-01.",
+    )
+    def retrieve(self, request, *args, **kwargs):
+        return super().retrieve(request, *args, **kwargs)
+
 
 class QuestionnaireAnswerViewSet(
     viewsets.ReadOnlyModelViewSet,
     dojo_mixins.AnswerSubClassFieldsMixin,
+    DeprecationNoticeMixin,
 ):
+    deprecated = True
+    end_of_life_date = datetime(2026, 6, 1)
     serializer_class = serializers.QuestionnaireAnswerSerializer
     queryset = Answer.objects.none()
     filter_backends = (DjangoFilterBackend,)
@@ -3199,10 +3232,27 @@ class QuestionnaireAnswerViewSet(
     def get_queryset(self):
         return Answer.objects.all().order_by("id")
 
+    @extend_schema(
+        deprecated=True,
+        description="This endpoint is deprecated and will be removed on 2026-06-01.",
+    )
+    def list(self, request, *args, **kwargs):
+        return super().list(request, *args, **kwargs)
+
+    @extend_schema(
+        deprecated=True,
+        description="This endpoint is deprecated and will be removed on 2026-06-01.",
+    )
+    def retrieve(self, request, *args, **kwargs):
+        return super().retrieve(request, *args, **kwargs)
+
 
 class QuestionnaireGeneralSurveyViewSet(
     viewsets.ReadOnlyModelViewSet,
+    DeprecationNoticeMixin,
 ):
+    deprecated = True
+    end_of_life_date = datetime(2026, 6, 1)
     serializer_class = serializers.QuestionnaireGeneralSurveySerializer
     queryset = General_Survey.objects.none()
     filter_backends = (DjangoFilterBackend,)
@@ -3214,10 +3264,27 @@ class QuestionnaireGeneralSurveyViewSet(
     def get_queryset(self):
         return General_Survey.objects.all().order_by("id")
 
+    @extend_schema(
+        deprecated=True,
+        description="This endpoint is deprecated and will be removed on 2026-06-01.",
+    )
+    def list(self, request, *args, **kwargs):
+        return super().list(request, *args, **kwargs)
+
+    @extend_schema(
+        deprecated=True,
+        description="This endpoint is deprecated and will be removed on 2026-06-01.",
+    )
+    def retrieve(self, request, *args, **kwargs):
+        return super().retrieve(request, *args, **kwargs)
+
 
 class QuestionnaireEngagementSurveyViewSet(
     viewsets.ReadOnlyModelViewSet,
+    DeprecationNoticeMixin,
 ):
+    deprecated = True
+    end_of_life_date = datetime(2026, 6, 1)
     serializer_class = serializers.QuestionnaireEngagementSurveySerializer
     queryset = Engagement_Survey.objects.none()
     filter_backends = (DjangoFilterBackend,)
@@ -3230,13 +3297,29 @@ def get_queryset(self):
         return Engagement_Survey.objects.all().order_by("id")
 
     @extend_schema(
-    request=OpenApiTypes.NONE,
-    parameters=[
-        OpenApiParameter(
-            "engagement_id", OpenApiTypes.INT, OpenApiParameter.PATH,
-        ),
-    ],
-    responses={status.HTTP_200_OK: serializers.QuestionnaireAnsweredSurveySerializer},
+        deprecated=True,
+        description="This endpoint is deprecated and will be removed on 2026-06-01.",
+    )
+    def list(self, request, *args, **kwargs):
+        return super().list(request, *args, **kwargs)
+
+    @extend_schema(
+        deprecated=True,
+        description="This endpoint is deprecated and will be removed on 2026-06-01.",
+    )
+    def retrieve(self, request, *args, **kwargs):
+        return super().retrieve(request, *args, **kwargs)
+
+    @extend_schema(
+        deprecated=True,
+        description="This endpoint is deprecated and will be removed on 2026-06-01.",
+        request=OpenApiTypes.NONE,
+        parameters=[
+            OpenApiParameter(
+                "engagement_id", OpenApiTypes.INT, OpenApiParameter.PATH,
+            ),
+        ],
+        responses={status.HTTP_200_OK: serializers.QuestionnaireAnsweredSurveySerializer},
     )
     @action(
         detail=True, methods=["post"], url_path=r"link_engagement/(?P<engagement_id>\d+)",
@@ -3258,7 +3341,10 @@ class QuestionnaireAnsweredSurveyViewSet(
     prefetch.PrefetchListMixin,
     prefetch.PrefetchRetrieveMixin,
     viewsets.ReadOnlyModelViewSet,
+    DeprecationNoticeMixin,
 ):
+    deprecated = True
+    end_of_life_date = datetime(2026, 6, 1)
     serializer_class = serializers.QuestionnaireAnsweredSurveySerializer
     queryset = Answered_Survey.objects.none()
     filter_backends = (DjangoFilterBackend,)
@@ -3270,6 +3356,20 @@ class QuestionnaireAnsweredSurveyViewSet(
     def get_queryset(self):
         return Answered_Survey.objects.all().order_by("id")
 
+    @extend_schema(
+        deprecated=True,
+        description="This endpoint is deprecated and will be removed on 2026-06-01.",
+    )
+    def list(self, request, *args, **kwargs):
+        return super().list(request, *args, **kwargs)
+
+    @extend_schema(
+        deprecated=True,
+        description="This endpoint is deprecated and will be removed on 2026-06-01.",
+    )
+    def retrieve(self, request, *args, **kwargs):
+        return super().retrieve(request, *args, **kwargs)
+
 
 # Authorization: configuration
 class AnnouncementViewSet(