diff --git a/IMPLEMENTATION_COVERAGE.md b/IMPLEMENTATION_COVERAGE.md
index 213775d83..f8ccf66d4 100644
--- a/IMPLEMENTATION_COVERAGE.md
+++ b/IMPLEMENTATION_COVERAGE.md
@@ -4767,7 +4767,7 @@
 - [X] move_account
 - [ ] remove_account_from_organization
 - [x] tag_resource
-- [ ] untag_resource
+- [x] untag_resource
 - [ ] update_organizational_unit
 - [ ] update_policy
 
diff --git a/moto/organizations/models.py b/moto/organizations/models.py
index b5059fe8d..2717d7ef8 100644
--- a/moto/organizations/models.py
+++ b/moto/organizations/models.py
@@ -467,5 +467,17 @@ class OrganizationsBackend(BaseBackend):
         tags = [{"Key": key, "Value": value} for key, value in account.tags.items()]
         return dict(Tags=tags)
 
+    def untag_resource(self, **kwargs):
+        account = next((a for a in self.accounts if a.id == kwargs["ResourceId"]), None)
+
+        if account is None:
+            raise RESTError(
+                "InvalidInputException",
+                "You provided a value that does not match the required pattern.",
+            )
+
+        for key in kwargs["TagKeys"]:
+            account.tags.pop(key, None)
+
 
 organizations_backend = OrganizationsBackend()
diff --git a/moto/organizations/responses.py b/moto/organizations/responses.py
index ab01ffb8a..7c42eb4ec 100644
--- a/moto/organizations/responses.py
+++ b/moto/organizations/responses.py
@@ -129,3 +129,8 @@ class OrganizationsResponse(BaseResponse):
         return json.dumps(
             self.organizations_backend.list_tags_for_resource(**self.request_params)
         )
+
+    def untag_resource(self):
+        return json.dumps(
+            self.organizations_backend.untag_resource(**self.request_params)
+        )
diff --git a/tests/test_organizations/test_organizations_boto3.py b/tests/test_organizations/test_organizations_boto3.py
index 27989c276..fb3ab3b24 100644
--- a/tests/test_organizations/test_organizations_boto3.py
+++ b/tests/test_organizations/test_organizations_boto3.py
@@ -676,3 +676,40 @@ def test_list_tags_for_resource_errors():
     ex.response["Error"]["Message"].should.contain(
         "You provided a value that does not match the required pattern."
     )
+
+
+@mock_organizations
+def test_untag_resource():
+    client = boto3.client("organizations", region_name="us-east-1")
+    client.create_organization(FeatureSet="ALL")
+    account_id = client.create_account(AccountName=mockname, Email=mockemail)[
+        "CreateAccountStatus"
+    ]["AccountId"]
+    client.tag_resource(ResourceId=account_id, Tags=[{"Key": "key", "Value": "value"}])
+    response = client.list_tags_for_resource(ResourceId=account_id)
+    response["Tags"].should.equal([{"Key": "key", "Value": "value"}])
+
+    # removing a non existing tag should not raise any error
+    client.untag_resource(ResourceId=account_id, TagKeys=["not-existing"])
+    response = client.list_tags_for_resource(ResourceId=account_id)
+    response["Tags"].should.equal([{"Key": "key", "Value": "value"}])
+
+    client.untag_resource(ResourceId=account_id, TagKeys=["key"])
+    response = client.list_tags_for_resource(ResourceId=account_id)
+    response["Tags"].should.have.length_of(0)
+
+
+@mock_organizations
+def test_untag_resource_errors():
+    client = boto3.client("organizations", region_name="us-east-1")
+    client.create_organization(FeatureSet="ALL")
+
+    with assert_raises(ClientError) as e:
+        client.untag_resource(ResourceId="000000000000", TagKeys=["key"])
+    ex = e.exception
+    ex.operation_name.should.equal("UntagResource")
+    ex.response["Error"]["Code"].should.equal("400")
+    ex.response["Error"]["Message"].should.contain("InvalidInputException")
+    ex.response["Error"]["Message"].should.contain(
+        "You provided a value that does not match the required pattern."
+    )