diff --git a/service/src/structure_comparer/data/mapping.py b/service/src/structure_comparer/data/mapping.py
index c1fc229..f29d5e0 100644
--- a/service/src/structure_comparer/data/mapping.py
+++ b/service/src/structure_comparer/data/mapping.py
@@ -113,7 +113,12 @@ def classify_remark_field(
             if self.action in EXTRA_ACTIONS:
 
                 # Cut away the common part with the parent and add the remainder to the parent's extra
-                self.other = parent_update.other + self.name[len(self.name_parent) :]
+                if parent_update.other is not None:
+                    self.other = (
+                        parent_update.other + self.name[len(self.name_parent) :]
+                    )
+                else:
+                    raise ValueError("Error with the data: parent_update.other is None")
                 self.remark = REMARKS[self.action].format(self.other)
 
             # Else use the parent's remark
diff --git a/service/src/structure_comparer/data/profile.py b/service/src/structure_comparer/data/profile.py
index b954c02..a4c578a 100644
--- a/service/src/structure_comparer/data/profile.py
+++ b/service/src/structure_comparer/data/profile.py
@@ -165,7 +165,7 @@ def ref_types(self) -> list[str]:
             [
                 p
                 for t in self.__data.type
-                if t.code == "Reference"
+                if t.code == "Reference" and t.targetProfile is not None
                 for p in t.targetProfile
             ]
             if self.__data.type is not None
diff --git a/service/src/structure_comparer/data/project.py b/service/src/structure_comparer/data/project.py
index f840e42..a10775e 100644
--- a/service/src/structure_comparer/data/project.py
+++ b/service/src/structure_comparer/data/project.py
@@ -23,7 +23,7 @@ def __init__(self, path: Path):
 
         self.__load_packages()
         self.load_comparisons()
-        self.__load_mappings()
+        self.load_mappings()
         self.__read_manual_entries()
 
     def __load_packages(self) -> None:
@@ -53,7 +53,7 @@ def load_comparisons(self):
             c.id: Comparison(c, self).init_ext() for c in self.config.comparisons
         }
 
-    def __load_mappings(self):
+    def load_mappings(self):
         self.mappings = {
             m.id: Mapping(m, self).init_ext() for m in self.config.mappings
         }
diff --git a/service/src/structure_comparer/handler/mapping.py b/service/src/structure_comparer/handler/mapping.py
index 9b9ca65..b27522a 100644
--- a/service/src/structure_comparer/handler/mapping.py
+++ b/service/src/structure_comparer/handler/mapping.py
@@ -1,4 +1,6 @@
+from datetime import datetime
 from typing import List
+from uuid import uuid4
 
 from ..action import Action
 from ..data.mapping import MappingField
@@ -14,11 +16,16 @@
 from ..helpers import get_field_by_name
 from ..model.manual_entries import ManualEntriesMapping
 from ..model.mapping import MappingBase as MappingBaseModel
+from ..model.mapping import MappingCreate as MappingCreateModel
 from ..model.mapping import MappingDetails as MappingDetailsModel
 from ..model.mapping import MappingField as MappingFieldModel
 from ..model.mapping import MappingFieldBase as MappingFieldBaseModel
 from ..model.mapping import MappingFieldMinimal as MappingFieldMinimalModel
 from ..model.mapping import MappingFieldsOutput as MappingFieldsOutputModel
+from ..data.config import MappingConfig as MappingConfigModel
+from ..data.config import ComparisonProfilesConfig as ComparisonProfilesConfigModel
+from ..data.config import ComparisonProfileConfig as ComparisonProfileConfigModel
+from ..data.mapping import Mapping as MappingModel
 from .project import ProjectsHandler
 
 
@@ -126,6 +133,39 @@ def set_field(
 
         return new_entry
 
+    def create_new(
+        self, project_key, mapping: MappingCreateModel
+    ) -> MappingDetailsModel:
+        proj = self.project_handler._get(project_key)
+        if proj is None:
+            raise ProjectNotFound()
+
+        new_mappingConfig = MappingConfigModel(
+            id=str(uuid4()),
+            version="1.0",
+            last_updated=datetime.now().isoformat(),
+            status="active",
+            mappings=ComparisonProfilesConfigModel(
+                sourceprofiles=[
+                    self._to_profiles_config(id) for id in mapping.source_ids
+                ],
+                targetprofile=self._to_profiles_config(mapping.target_id),
+            ),
+        )
+        new_mapping = MappingModel(new_mappingConfig, proj)
+        new_mapping.fill_action_remark(proj.manual_entries)
+
+        proj.config.mappings.append(new_mappingConfig)
+        proj.write_config()
+        proj.load_mappings()
+
+        mapping = proj.mappings.get(new_mapping.id)
+        return mapping.to_details_model()
+
+    def _to_profiles_config(self, url: str) -> ComparisonProfileConfigModel:
+        url, version = url.split("|")
+        return ComparisonProfileConfigModel(url=url, version=version)
+
     def __get(self, project_key, mapping_id, proj: Project | None = None):
         if proj is None:
             proj = self.project_handler._get(project_key)
diff --git a/service/src/structure_comparer/model/mapping.py b/service/src/structure_comparer/model/mapping.py
index f01c7b2..657ab1e 100644
--- a/service/src/structure_comparer/model/mapping.py
+++ b/service/src/structure_comparer/model/mapping.py
@@ -37,6 +37,11 @@ class MappingBase(BaseModel):
     target: Profile
 
 
+class MappingCreate(BaseModel):
+    source_ids: list[str]
+    target_id: str
+
+
 class MappingDetails(MappingBase):
     fields: list[MappingField]
 
diff --git a/service/src/structure_comparer/serve.py b/service/src/structure_comparer/serve.py
index 05eb328..5f3568c 100644
--- a/service/src/structure_comparer/serve.py
+++ b/service/src/structure_comparer/serve.py
@@ -36,6 +36,7 @@
 from .model.get_mappings_output import GetMappingsOutput
 from .model.init_project_input import InitProjectInput
 from .model.mapping import MappingBase as MappingBaseModel
+from .model.mapping import MappingCreate as MappingCreateModel
 from .model.mapping import MappingDetails as MappingDetailsModel
 from .model.mapping import MappingField as MappingFieldModel
 from .model.mapping import MappingFieldMinimal as MappingFieldMinimalModel
@@ -993,6 +994,63 @@ async def get_mapping_field(
         return ErrorModel.from_except(e)
 
 
+@app.post(
+    "/project/{project_key}/mapping",
+    tags=["Mappings"],
+    response_model_exclude_unset=True,
+    response_model_exclude_none=True,
+    responses={400: {}, 404: {}},
+)
+async def post_mapping(
+    project_key: str,
+    mappingData: MappingCreateModel,
+    response: Response,
+) -> MappingDetailsModel | ErrorModel:
+    """
+    Post a new mapping for a project
+    Creates a new mapping in the project with the given key.
+    The mapping needs to be a valid MappingBaseModel.
+
+    ---
+    consumes:
+      - application/json
+    parameters:
+      - in: path
+        name: project_key
+        type: string
+        required: true
+        description: The key of the project
+    responses:
+      200:
+        description: The mapping was created
+      400:
+        description: There was something wrong with the request
+        schema:
+          properties:
+            error:
+              type: string
+              description: An error message
+      404:
+        description: Project not found
+    """
+    global mapping_handler
+    try:
+        return mapping_handler.create_new(project_key, mappingData)
+
+    except ProjectNotFound as e:
+        response.status_code = 404
+        return ErrorModel.from_except(e)
+
+    except (
+        MappingActionNotAllowed,
+        MappingTargetMissing,
+        MappingTargetNotFound,
+        MappingValueMissing,
+    ) as e:
+        response.status_code = 400
+        return ErrorModel.from_except(e)
+
+
 @app.post(
     "/mapping/{mapping_id}/field/{field_id}/classification",
     tags=["Fields"],