diff --git a/CHANGELOG.md b/CHANGELOG.md
index d86b71a..e704038 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -38,6 +38,7 @@ drc restart migrations; drc logs -ft --tail=200 migrations
 - Fix query for organizations report [OP-3636]
 - Bump report-generation-service to most recent version
 - Write migration to harmonize date formats of change events [OP-3559]
+- datafix: cleanup of duplicate memberships [OP-3634]
 ### Deploy notes
 ```
 drc pull deltanotifier; drc up -d deltanotifier
diff --git a/config/migrations/2025/20250725120411-fix-reversed-memberships-ocmw-municipality.sparql b/config/migrations/2025/20250725120411-fix-reversed-memberships-ocmw-municipality.sparql
new file mode 100644
index 0000000..a170150
--- /dev/null
+++ b/config/migrations/2025/20250725120411-fix-reversed-memberships-ocmw-municipality.sparql
@@ -0,0 +1,40 @@
+PREFIX org: <http://www.w3.org/ns/org#>
+PREFIX mu: <http://mu.semte.ch/vocabularies/core/>
+
+DELETE {
+  GRAPH <http://mu.semte.ch/graphs/administrative-unit> {
+    ?membership org:organization ?ocmw ;
+                org:member ?municipality .
+  }
+}
+INSERT {
+  GRAPH <http://mu.semte.ch/graphs/administrative-unit> {
+    ?membership org:organization ?municipality ;
+                org:member ?ocmw .
+  }
+}
+WHERE {
+  GRAPH <http://mu.semte.ch/graphs/administrative-unit> {
+    ?membership a org:Membership ;
+      org:organization ?ocmw ;
+      org:member ?municipality ;
+      org:role <http://data.lblod.info/id/rollen/4ec7d5c39bdc4e84b4174379b9e22ad8> .
+  }
+
+  GRAPH ?graphMunicipality {
+    ?municipality org:classification <http://data.vlaanderen.be/id/concept/BestuurseenheidClassificatieCode/5ab0e9b8a3b2ca7c5e000001> .
+  }
+
+  GRAPH ?graphOCMW {
+    ?ocmw org:classification <http://data.vlaanderen.be/id/concept/BestuurseenheidClassificatieCode/5ab0e9b8a3b2ca7c5e000002> .
+  }
+
+  FILTER NOT EXISTS {
+    GRAPH <http://mu.semte.ch/graphs/administrative-unit> {
+      ?correctMembership a org:Membership ;
+        org:organization ?municipality ;
+        org:member ?ocmw ;
+        org:role <http://data.lblod.info/id/rollen/4ec7d5c39bdc4e84b4174379b9e22ad8> .
+    }
+  }
+}
diff --git a/config/migrations/2025/20250725120522-remove-duplicate-memberships-ocmw-municipality.sparql b/config/migrations/2025/20250725120522-remove-duplicate-memberships-ocmw-municipality.sparql
new file mode 100644
index 0000000..209b394
--- /dev/null
+++ b/config/migrations/2025/20250725120522-remove-duplicate-memberships-ocmw-municipality.sparql
@@ -0,0 +1,33 @@
+PREFIX org: <http://www.w3.org/ns/org#>
+PREFIX mu: <http://mu.semte.ch/vocabularies/core/>
+
+DELETE {
+  GRAPH <http://mu.semte.ch/graphs/administrative-unit> {
+    ?duplicateMembership ?p ?o .
+  }
+} WHERE {
+  GRAPH <http://mu.semte.ch/graphs/administrative-unit> {
+    ?duplicateMembership a org:Membership ;
+      org:organization ?ocmw ;
+      org:member ?municipality ;
+      org:role <http://data.lblod.info/id/rollen/4ec7d5c39bdc4e84b4174379b9e22ad8> ;
+      ?p ?o .
+
+    # Find the other memberships with swapped organizations
+    ?correctMembership a org:Membership ;
+      org:organization ?municipality ;
+      org:member ?ocmw ;
+      org:role <http://data.lblod.info/id/rollen/4ec7d5c39bdc4e84b4174379b9e22ad8> .
+  }
+
+  GRAPH <http://mu.semte.ch/graphs/shared> {
+    ?municipality org:classification ?municipalityClassification .
+  }
+
+  GRAPH <http://mu.semte.ch/graphs/administrative-unit> {
+    ?ocmw org:classification ?ocmwClassification .
+  }
+
+  FILTER(?municipalityClassification = <http://data.vlaanderen.be/id/concept/BestuurseenheidClassificatieCode/5ab0e9b8a3b2ca7c5e000001>)
+  FILTER(?ocmwClassification = <http://data.vlaanderen.be/id/concept/BestuurseenheidClassificatieCode/5ab0e9b8a3b2ca7c5e000002>)
+}