diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8da75d3b1..b793bedeb 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 
+- Add namespace support to `DataCube.process`, `PGNode`, `ProcessGraphVisitor` (minor API breaking change) and related. Allows building process graphs that with processes from non-"backend" namespaces ([#182](https://github.com/Open-EO/openeo-python-client/issues/182))
+
 ### Changed
 
 ### Removed
diff --git a/openeo/_version.py b/openeo/_version.py
index 0d7fdf989..2198e590a 100644
--- a/openeo/_version.py
+++ b/openeo/_version.py
@@ -1 +1 @@
-__version__ = '0.4.11a1'
+__version__ = '0.5.0a1'
diff --git a/openeo/internal/graph_building.py b/openeo/internal/graph_building.py
index 15d699353..eb83edaa9 100644
--- a/openeo/internal/graph_building.py
+++ b/openeo/internal/graph_building.py
@@ -8,7 +8,7 @@
 
 from openeo.api.process import Parameter
 from openeo.internal.process_graph_visitor import ProcessGraphVisitor
-from openeo.util import legacy_alias
+from openeo.util import legacy_alias, dict_no_none
 
 
 class PGNode:
@@ -24,7 +24,7 @@ class PGNode:
 
     """
 
-    def __init__(self, process_id: str, arguments: dict = None, **kwargs):
+    def __init__(self, process_id: str, arguments: dict = None, namespace: Union[str, None] = None, **kwargs):
         self._process_id = process_id
         # Merge arguments dict and kwargs
         arguments = dict(**(arguments or {}), **kwargs)
@@ -34,6 +34,7 @@ def __init__(self, process_id: str, arguments: dict = None, **kwargs):
                 arguments[arg] = {"from_node": value}
         # TODO: use a frozendict of some sort to ensure immutability?
         self._arguments = arguments
+        self._namespace = namespace
 
     def __repr__(self):
         return "<{c} {p!r} at 0x{m:x}>".format(c=self.__class__.__name__, p=self.process_id, m=id(self))
@@ -46,6 +47,10 @@ def process_id(self) -> str:
     def arguments(self) -> dict:
         return self._arguments
 
+    @property
+    def namespace(self) -> Union[str, None]:
+        return self._namespace
+
     def to_dict(self) -> dict:
         """
         Convert process graph to a nested dictionary structure.
@@ -55,7 +60,7 @@ def to_dict(self) -> dict:
         def _deep_copy(x):
             """PGNode aware deep copy helper"""
             if isinstance(x, PGNode):
-                return {"process_id": x.process_id, "arguments": _deep_copy(x.arguments)}
+                return dict_no_none(process_id=x.process_id, arguments=_deep_copy(x.arguments), namespace=x.namespace)
             if isinstance(x, Parameter):
                 return {"from_parameter": x.name}
             elif isinstance(x, dict):
@@ -201,20 +206,21 @@ def accept_node(self, node: PGNode):
         # Process reused nodes only first time and remember node id.
         node_id = id(node)
         if node_id not in self._node_cache:
-            super()._accept_process(process_id=node.process_id, arguments=node.arguments)
+            super()._accept_process(process_id=node.process_id, arguments=node.arguments, namespace=node.namespace)
             self._node_cache[node_id] = self._last_node_id
         else:
             self._last_node_id = self._node_cache[node_id]
 
-    def enterProcess(self, process_id: str, arguments: dict):
+    def enterProcess(self, process_id: str, arguments: dict, namespace: Union[str, None]):
         self._argument_stack.append({})
 
-    def leaveProcess(self, process_id: str, arguments: dict):
+    def leaveProcess(self, process_id: str, arguments: dict, namespace: Union[str, None]):
         node_id = self._node_id_generator.generate(process_id)
-        self._flattened[node_id] = {
-            "process_id": process_id,
-            "arguments": self._argument_stack.pop()
-        }
+        self._flattened[node_id] = dict_no_none(
+            process_id=process_id,
+            arguments=self._argument_stack.pop(),
+            namespace=namespace,
+        )
         self._last_node_id = node_id
 
     def _store_argument(self, argument_id: str, value):
diff --git a/openeo/internal/process_graph_visitor.py b/openeo/internal/process_graph_visitor.py
index e96575c98..9e529489a 100644
--- a/openeo/internal/process_graph_visitor.py
+++ b/openeo/internal/process_graph_visitor.py
@@ -1,4 +1,5 @@
 from abc import ABC
+from typing import Union
 
 from deprecated import deprecated
 
@@ -75,11 +76,12 @@ def accept(self, node: dict):
     def accept_node(self, node: dict):
         pid = node['process_id']
         arguments = node.get('arguments', {})
-        self._accept_process(process_id=pid, arguments=arguments)
+        namespace = node.get("namespace", None)
+        self._accept_process(process_id=pid, arguments=arguments, namespace=namespace)
 
-    def _accept_process(self, process_id: str, arguments: dict):
+    def _accept_process(self, process_id: str, arguments: dict, namespace: Union[str, None]):
         self.process_stack.append(process_id)
-        self.enterProcess(process_id=process_id, arguments=arguments)
+        self.enterProcess(process_id=process_id, arguments=arguments, namespace=namespace)
         for arg_id, value in sorted(arguments.items()):
             if isinstance(value, list):
                 self.enterArray(argument_id=arg_id)
@@ -91,7 +93,7 @@ def _accept_process(self, process_id: str, arguments: dict):
                 self.leaveArgument(argument_id=arg_id, value=value)
             else:
                 self.constantArgument(argument_id=arg_id, value=value)
-        self.leaveProcess(process_id=process_id, arguments=arguments)
+        self.leaveProcess(process_id=process_id, arguments=arguments, namespace=namespace)
         assert self.process_stack.pop() == process_id
 
     def _accept_argument_list(self, elements: list):
@@ -121,10 +123,10 @@ def _accept_dict(self, value: dict):
     def from_parameter(self,parameter_id:str):
         pass
 
-    def enterProcess(self, process_id: str, arguments: dict):
+    def enterProcess(self, process_id: str, arguments: dict, namespace: Union[str, None]):
         pass
 
-    def leaveProcess(self, process_id: str, arguments: dict):
+    def leaveProcess(self, process_id: str, arguments: dict, namespace: Union[str, None]):
         pass
 
     def enterArgument(self, argument_id: str, value):
diff --git a/openeo/rest/datacube.py b/openeo/rest/datacube.py
index 8496a6a99..3e5d7dd13 100644
--- a/openeo/rest/datacube.py
+++ b/openeo/rest/datacube.py
@@ -93,12 +93,21 @@ def _api_version(self):
     def connection(self) -> 'openeo.Connection':
         return self._connection
 
-    def process(self, process_id: str, arguments: dict = None, metadata: CollectionMetadata = None, **kwargs) -> 'DataCube':
+    def process(
+            self,
+            process_id: str,
+            arguments: dict = None,
+            metadata: Optional[CollectionMetadata] = None,
+            namespace: Optional[str] = None,
+            **kwargs
+    ) -> 'DataCube':
         """
         Generic helper to create a new DataCube by applying a process.
 
         :param process_id: process id of the process.
         :param arguments: argument dictionary for the process.
+        :param metadata: optional: metadata to override original cube metadata (e.g. when reducing dimensions)
+        :param namespace: optional: process namespace
         :return: new DataCube instance
         """
         arguments = {**(arguments or {}), **kwargs}
@@ -110,16 +119,17 @@ def process(self, process_id: str, arguments: dict = None, metadata: CollectionM
         return self.process_with_node(PGNode(
             process_id=process_id,
             arguments=arguments,
+            namespace=namespace,
         ), metadata=metadata)
 
     graph_add_node = legacy_alias(process, "graph_add_node")
 
-    def process_with_node(self, pg: PGNode, metadata: CollectionMetadata = None) -> 'DataCube':
+    def process_with_node(self, pg: PGNode, metadata: Optional[CollectionMetadata] = None) -> 'DataCube':
         """
         Generic helper to create a new DataCube by applying a process (given as process graph node)
 
         :param pg: process graph node (containing process id and arguments)
-        :param metadata: (optional) metadata to override original cube metadata (e.g. when reducing dimensions)
+        :param metadata: optional: metadata to override original cube metadata (e.g. when reducing dimensions)
         :return: new DataCube instance
         """
         # TODO: deep copy `self.metadata` instead of using same instance?
diff --git a/tests/data/1.0.0/process_foo_namespaced.json b/tests/data/1.0.0/process_foo_namespaced.json
new file mode 100644
index 000000000..0a4227609
--- /dev/null
+++ b/tests/data/1.0.0/process_foo_namespaced.json
@@ -0,0 +1,21 @@
+{
+  "loadcollection1": {
+    "process_id": "load_collection",
+    "arguments": {
+      "id": "S2",
+      "spatial_extent": null,
+      "temporal_extent": null
+    }
+  },
+  "foo1": {
+    "process_id": "foo",
+    "namespace": "bar",
+    "arguments": {
+      "data": {
+        "from_node": "loadcollection1"
+      },
+      "bar": 123
+    },
+    "result": true
+  }
+}
diff --git a/tests/internal/test_graphbuilding.py b/tests/internal/test_graphbuilding.py
index 4bbdc8644..31027ec07 100644
--- a/tests/internal/test_graphbuilding.py
+++ b/tests/internal/test_graphbuilding.py
@@ -19,6 +19,11 @@ def test_pgnode_arguments():
         PGNode("foo", arguments={"bar": 123}, bar=456)
 
 
+def test_pgnode_namespace():
+    assert PGNode("foo").namespace is None
+    assert PGNode("foo", namespace="bar").namespace == "bar"
+
+
 def test_pgnode_to_dict():
     pg = PGNode(process_id="load_collection", arguments={"collection_id": "S2"})
     assert pg.to_dict() == {
@@ -27,6 +32,15 @@ def test_pgnode_to_dict():
     }
 
 
+def test_pgnode_to_dict_namespace():
+    pg = PGNode(process_id="load_collection", arguments={"collection_id": "S2"}, namespace="bar")
+    assert pg.to_dict() == {
+        "process_id": "load_collection",
+        "namespace": "bar",
+        "arguments": {"collection_id": "S2"}
+    }
+
+
 def test_pgnode_to_dict_nested():
     pg = PGNode(
         process_id="filter_bands",
@@ -88,6 +102,11 @@ def test_build_and_flatten_argument_dict():
     assert node.flat_graph() == {"foo1": {"process_id": "foo", "arguments": {"bar": "red", "x": 3}, "result": True}}
 
 
+def test_build_and_flatten_namespace():
+    node = PGNode("foo", namespace="bar")
+    assert node.flat_graph() == {"foo1": {"process_id": "foo", "namespace": "bar", "arguments": {}, "result": True}}
+
+
 def test_pgnode_to_dict_subprocess_graphs():
     load_collection = PGNode("load_collection", collection_id="S2")
     band2 = PGNode("array_element", data={"from_argument": "data"}, index=2)
diff --git a/tests/internal/test_process_graph_visitor.py b/tests/internal/test_process_graph_visitor.py
index 52fd8d981..43b3bd6e1 100644
--- a/tests/internal/test_process_graph_visitor.py
+++ b/tests/internal/test_process_graph_visitor.py
@@ -1,4 +1,3 @@
-from unittest import TestCase
 from unittest.mock import MagicMock, call, ANY
 
 import pytest
@@ -16,7 +15,26 @@ def test_visit_node():
     visitor.enterArgument = MagicMock()
     visitor.accept_node(node)
 
-    assert visitor.enterProcess.call_args_list == [call(process_id="cos", arguments={"x": {"from_argument": "data"}})]
+    assert visitor.enterProcess.call_args_list == [
+        call(process_id="cos", arguments={"x": {"from_argument": "data"}}, namespace=None)
+    ]
+    assert visitor.enterArgument.call_args_list == [call(argument_id="x", value={"from_argument": "data"})]
+
+
+def test_visit_node_namespaced():
+    node = {
+        "process_id": "cos",
+        "namespace": "math",
+        "arguments": {"x": {"from_argument": "data"}}
+    }
+    visitor = ProcessGraphVisitor()
+    visitor.enterProcess = MagicMock()
+    visitor.enterArgument = MagicMock()
+    visitor.accept_node(node)
+
+    assert visitor.enterProcess.call_args_list == [
+        call(process_id="cos", arguments={"x": {"from_argument": "data"}}, namespace="math")
+    ]
     assert visitor.enterArgument.call_args_list == [call(argument_id="x", value={"from_argument": "data"})]
 
 
@@ -51,8 +69,8 @@ def test_visit_nodes():
     visitor.accept_process_graph(graph)
 
     assert visitor.leaveProcess.call_args_list == [
-        call(process_id="abs", arguments=ANY),
-        call(process_id="cos", arguments=ANY),
+        call(process_id="abs", arguments=ANY, namespace=None),
+        call(process_id="cos", arguments=ANY, namespace=None),
     ]
     assert visitor.enterArgument.call_args_list == [
         call(argument_id="data", value=ANY),
@@ -93,8 +111,8 @@ def test_visit_nodes_array():
 
     visitor.accept_process_graph(graph)
     assert visitor.leaveProcess.call_args_list == [
-        call(process_id='abs', arguments=ANY),
-        call(process_id='cos', arguments=ANY)
+        call(process_id='abs', arguments=ANY, namespace=None),
+        call(process_id='cos', arguments=ANY, namespace=None)
     ]
     assert visitor.enterArgument.call_args_list == [
         call(argument_id="data", value=ANY)
@@ -130,8 +148,8 @@ def test_visit_array_with_dereferenced_nodes():
 
     visitor.accept_node(dereferenced)
     assert visitor.leaveProcess.call_args_list == [
-        call(process_id='array_element', arguments=ANY),
-        call(process_id='product', arguments=ANY)
+        call(process_id='array_element', arguments=ANY, namespace=None),
+        call(process_id='product', arguments=ANY, namespace=None)
     ]
     assert visitor.enterArgument.call_args_list == [
         call(argument_id="data", value={'from_argument': 'data'})
diff --git a/tests/rest/datacube/test_datacube100.py b/tests/rest/datacube/test_datacube100.py
index e7fbba79f..4e675e051 100644
--- a/tests/rest/datacube/test_datacube100.py
+++ b/tests/rest/datacube/test_datacube100.py
@@ -539,12 +539,18 @@ def test_custom_process_kwargs_datacube_pg(con100: Connection):
     assert res.graph == expected
 
 
-def test_custom_process_kwargs_datacube_chained(con100: Connection):
+def test_custom_process_kwargs_this(con100: Connection):
     res = con100.load_collection("S2").process(process_id="foo", data=THIS, bar=123)
     expected = load_json_resource('data/1.0.0/process_foo.json')
     assert res.graph == expected
 
 
+def test_custom_process_kwargs_namespaced(con100: Connection):
+    res = con100.load_collection("S2").process(process_id="foo", data=THIS, bar=123, namespace="bar")
+    expected = load_json_resource('data/1.0.0/process_foo_namespaced.json')
+    assert res.graph == expected
+
+
 def test_custom_process_arguments_datacube(con100: Connection):
     img = con100.load_collection("S2")
     res = img.process(process_id="foo", arguments={"data": img, "bar": 123})
@@ -559,12 +565,18 @@ def test_custom_process_arguments_datacube_pg(con100: Connection):
     assert res.graph == expected
 
 
-def test_custom_process_arguments_datacube_chained(con100: Connection):
+def test_custom_process_arguments_this(con100: Connection):
     res = con100.load_collection("S2").process(process_id="foo", arguments={"data": THIS, "bar": 123})
     expected = load_json_resource('data/1.0.0/process_foo.json')
     assert res.graph == expected
 
 
+def test_custom_process_arguments_namespacd(con100: Connection):
+    res = con100.load_collection("S2").process(process_id="foo", arguments={"data": THIS, "bar": 123}, namespace="bar")
+    expected = load_json_resource('data/1.0.0/process_foo_namespaced.json')
+    assert res.graph == expected
+
+
 def test_save_user_defined_process(con100, requests_mock):
     requests_mock.get(API_URL + "/processes", json={"processes": [{"id": "add"}]})