diff --git a/integrations/mattermost/manifest.yaml b/integrations/mattermost/manifest.yaml
new file mode 100644
index 0000000..e1a5f02
--- /dev/null
+++ b/integrations/mattermost/manifest.yaml
@@ -0,0 +1,80 @@
+id: mattermost
+name: Mattermost
+version: 1.0.0
+description: "Mattermost (REST API v4) — SOC ChatOps: create posts, look up channels by name, search posts, create channels, and look up users. Bearer-token authentication; stdlib-only, no extra Python dependencies."
+changelog: "1.0.0 — Initial release: create post, get channel by name, search posts, create channel, get user."
+category: notification
+
+# Per-instance configuration. Auth header 'Authorization: Bearer <token>'.
+config_schema:
+  properties:
+    base_url:
+      type: string
+      description: "Mattermost server URL (e.g. https://mm.example.com)"
+    token:
+      type: string
+      description: "Personal access / bot token"
+      x-soar-sensitive: true
+  required:
+    - base_url
+    - token
+
+commands:
+  - id: create_post
+    name: mattermost-create-post
+    description: "Create a post in a channel."
+    inputs_schema:
+      properties:
+        channel_id: { type: string, description: "Channel ID" }
+        message: { type: string, description: "Message text (Markdown supported)" }
+      required: [channel_id, message]
+    outputs_schema: { properties: {} }
+  - id: get_channel_by_name
+    name: mattermost-get-channel-by-name
+    description: "Get a channel by team name and channel name."
+    risk: read
+    inputs_schema:
+      properties:
+        team_name: { type: string, description: "Team name" }
+        channel_name: { type: string, description: "Channel name" }
+      required: [team_name, channel_name]
+    outputs_schema: { properties: {} }
+  - id: search_posts
+    name: mattermost-search-posts
+    description: "Search posts within a team."
+    risk: read
+    inputs_schema:
+      properties:
+        team_id: { type: string, description: "Team ID" }
+        terms: { type: string, description: "Search terms" }
+      required: [team_id, terms]
+    outputs_schema: { properties: {} }
+  - id: create_channel
+    name: mattermost-create-channel
+    description: "Create a channel."
+    inputs_schema:
+      properties:
+        team_id: { type: string, description: "Team ID" }
+        name: { type: string, description: "Channel URL name (lowercase)" }
+        display_name: { type: string, description: "Display name" }
+        channel_type: { type: string, description: "O (public) or P (private), default O" }
+      required: [team_id, name, display_name]
+    outputs_schema: { properties: {} }
+  - id: get_user
+    name: mattermost-get-user
+    description: "Look up a user by username."
+    risk: read
+    inputs_schema:
+      properties:
+        username: { type: string, description: "Username" }
+      required: [username]
+    outputs_schema: { properties: {} }
+
+  - id: test_connection
+    name: mattermost-test-connection
+    description: "Verify connectivity and the token (used by the Test button)."
+    risk: read
+    inputs_schema:
+      properties: {}
+      required: []
+    outputs_schema: { properties: {} }
diff --git a/integrations/mattermost/scripts/create_channel.py b/integrations/mattermost/scripts/create_channel.py
new file mode 100644
index 0000000..f7f3fce
--- /dev/null
+++ b/integrations/mattermost/scripts/create_channel.py
@@ -0,0 +1,64 @@
+import json, os, sys, urllib.parse, urllib.request, urllib.error
+
+
+def _cfg():
+    return json.loads(os.environ.get("INTEGRATION_SECRETS", "{}"))
+
+
+def _inputs():
+    return json.loads(os.environ.get("INTEGRATION_INPUTS", "{}"))
+
+
+def request(method, path, cfg, body=None, params=None):
+    url = str(cfg.get("base_url", "")).rstrip("/") + "/api/v4" + path
+    if params:
+        clean = {k: v for k, v in params.items() if v not in (None, "")}
+        if clean:
+            url += "?" + urllib.parse.urlencode(clean)
+    data = json.dumps(body).encode("utf-8") if body is not None else None
+    headers = {"Authorization": "Bearer " + str(cfg.get("token", "")), "Accept": "application/json"}
+    if data is not None:
+        headers["Content-Type"] = "application/json"
+    req = urllib.request.Request(url, data=data, headers=headers, method=method)
+    with urllib.request.urlopen(req, timeout=60) as r:
+        raw = r.read()
+        return json.loads(raw) if raw else {}
+
+
+def _run(fn):
+    try:
+        print(json.dumps(fn(_cfg(), _inputs())))
+    except urllib.error.HTTPError as e:
+        print(json.dumps({"error": "HTTP " + str(e.code), "detail": e.read().decode("utf-8", "replace")}))
+        sys.exit(1)
+    except Exception as e:
+        print(json.dumps({"error": str(e)}))
+        sys.exit(1)
+
+
+def main(cfg, inputs):
+    team_id = inputs.get("team_id")
+    name = inputs.get("name")
+    display_name = inputs.get("display_name")
+    channel_type = inputs.get("channel_type")
+    if not team_id:
+        raise Exception("team_id is required")
+    if not name:
+        raise Exception("name is required")
+    if not display_name:
+        raise Exception("display_name is required")
+
+    return request(
+        "POST",
+        "/channels",
+        cfg,
+        body={
+            "team_id": team_id,
+            "name": name,
+            "display_name": display_name,
+            "type": (channel_type or "O"),
+        },
+    )
+
+
+_run(main)
diff --git a/integrations/mattermost/scripts/create_post.py b/integrations/mattermost/scripts/create_post.py
new file mode 100644
index 0000000..16d7059
--- /dev/null
+++ b/integrations/mattermost/scripts/create_post.py
@@ -0,0 +1,50 @@
+import json, os, sys, urllib.parse, urllib.request, urllib.error
+
+
+def _cfg():
+    return json.loads(os.environ.get("INTEGRATION_SECRETS", "{}"))
+
+
+def _inputs():
+    return json.loads(os.environ.get("INTEGRATION_INPUTS", "{}"))
+
+
+def request(method, path, cfg, body=None, params=None):
+    url = str(cfg.get("base_url", "")).rstrip("/") + "/api/v4" + path
+    if params:
+        clean = {k: v for k, v in params.items() if v not in (None, "")}
+        if clean:
+            url += "?" + urllib.parse.urlencode(clean)
+    data = json.dumps(body).encode("utf-8") if body is not None else None
+    headers = {"Authorization": "Bearer " + str(cfg.get("token", "")), "Accept": "application/json"}
+    if data is not None:
+        headers["Content-Type"] = "application/json"
+    req = urllib.request.Request(url, data=data, headers=headers, method=method)
+    with urllib.request.urlopen(req, timeout=60) as r:
+        raw = r.read()
+        return json.loads(raw) if raw else {}
+
+
+def _run(fn):
+    try:
+        print(json.dumps(fn(_cfg(), _inputs())))
+    except urllib.error.HTTPError as e:
+        print(json.dumps({"error": "HTTP " + str(e.code), "detail": e.read().decode("utf-8", "replace")}))
+        sys.exit(1)
+    except Exception as e:
+        print(json.dumps({"error": str(e)}))
+        sys.exit(1)
+
+
+def main(cfg, inputs):
+    channel_id = inputs.get("channel_id")
+    message = inputs.get("message")
+    if not channel_id:
+        raise Exception("channel_id is required")
+    if not message:
+        raise Exception("message is required")
+
+    return request("POST", "/posts", cfg, body={"channel_id": channel_id, "message": message})
+
+
+_run(main)
diff --git a/integrations/mattermost/scripts/get_channel_by_name.py b/integrations/mattermost/scripts/get_channel_by_name.py
new file mode 100644
index 0000000..f2d129f
--- /dev/null
+++ b/integrations/mattermost/scripts/get_channel_by_name.py
@@ -0,0 +1,51 @@
+import json, os, sys, urllib.parse, urllib.request, urllib.error
+
+
+def _cfg():
+    return json.loads(os.environ.get("INTEGRATION_SECRETS", "{}"))
+
+
+def _inputs():
+    return json.loads(os.environ.get("INTEGRATION_INPUTS", "{}"))
+
+
+def request(method, path, cfg, body=None, params=None):
+    url = str(cfg.get("base_url", "")).rstrip("/") + "/api/v4" + path
+    if params:
+        clean = {k: v for k, v in params.items() if v not in (None, "")}
+        if clean:
+            url += "?" + urllib.parse.urlencode(clean)
+    data = json.dumps(body).encode("utf-8") if body is not None else None
+    headers = {"Authorization": "Bearer " + str(cfg.get("token", "")), "Accept": "application/json"}
+    if data is not None:
+        headers["Content-Type"] = "application/json"
+    req = urllib.request.Request(url, data=data, headers=headers, method=method)
+    with urllib.request.urlopen(req, timeout=60) as r:
+        raw = r.read()
+        return json.loads(raw) if raw else {}
+
+
+def _run(fn):
+    try:
+        print(json.dumps(fn(_cfg(), _inputs())))
+    except urllib.error.HTTPError as e:
+        print(json.dumps({"error": "HTTP " + str(e.code), "detail": e.read().decode("utf-8", "replace")}))
+        sys.exit(1)
+    except Exception as e:
+        print(json.dumps({"error": str(e)}))
+        sys.exit(1)
+
+
+def main(cfg, inputs):
+    team_name = inputs.get("team_name")
+    channel_name = inputs.get("channel_name")
+    if not team_name:
+        raise Exception("team_name is required")
+    if not channel_name:
+        raise Exception("channel_name is required")
+
+    q = lambda v: urllib.parse.quote(str(v), safe="")
+    return request("GET", "/teams/name/" + q(team_name) + "/channels/name/" + q(channel_name), cfg)
+
+
+_run(main)
diff --git a/integrations/mattermost/scripts/get_user.py b/integrations/mattermost/scripts/get_user.py
new file mode 100644
index 0000000..1a993c5
--- /dev/null
+++ b/integrations/mattermost/scripts/get_user.py
@@ -0,0 +1,48 @@
+import json, os, sys, urllib.parse, urllib.request, urllib.error
+
+
+def _cfg():
+    return json.loads(os.environ.get("INTEGRATION_SECRETS", "{}"))
+
+
+def _inputs():
+    return json.loads(os.environ.get("INTEGRATION_INPUTS", "{}"))
+
+
+def request(method, path, cfg, body=None, params=None):
+    url = str(cfg.get("base_url", "")).rstrip("/") + "/api/v4" + path
+    if params:
+        clean = {k: v for k, v in params.items() if v not in (None, "")}
+        if clean:
+            url += "?" + urllib.parse.urlencode(clean)
+    data = json.dumps(body).encode("utf-8") if body is not None else None
+    headers = {"Authorization": "Bearer " + str(cfg.get("token", "")), "Accept": "application/json"}
+    if data is not None:
+        headers["Content-Type"] = "application/json"
+    req = urllib.request.Request(url, data=data, headers=headers, method=method)
+    with urllib.request.urlopen(req, timeout=60) as r:
+        raw = r.read()
+        return json.loads(raw) if raw else {}
+
+
+def _run(fn):
+    try:
+        print(json.dumps(fn(_cfg(), _inputs())))
+    except urllib.error.HTTPError as e:
+        print(json.dumps({"error": "HTTP " + str(e.code), "detail": e.read().decode("utf-8", "replace")}))
+        sys.exit(1)
+    except Exception as e:
+        print(json.dumps({"error": str(e)}))
+        sys.exit(1)
+
+
+def main(cfg, inputs):
+    username = inputs.get("username")
+    if not username:
+        raise Exception("username is required")
+
+    q = lambda v: urllib.parse.quote(str(v), safe="")
+    return request("GET", "/users/username/" + q(username), cfg)
+
+
+_run(main)
diff --git a/integrations/mattermost/scripts/search_posts.py b/integrations/mattermost/scripts/search_posts.py
new file mode 100644
index 0000000..7d4f84b
--- /dev/null
+++ b/integrations/mattermost/scripts/search_posts.py
@@ -0,0 +1,56 @@
+import json, os, sys, urllib.parse, urllib.request, urllib.error
+
+
+def _cfg():
+    return json.loads(os.environ.get("INTEGRATION_SECRETS", "{}"))
+
+
+def _inputs():
+    return json.loads(os.environ.get("INTEGRATION_INPUTS", "{}"))
+
+
+def request(method, path, cfg, body=None, params=None):
+    url = str(cfg.get("base_url", "")).rstrip("/") + "/api/v4" + path
+    if params:
+        clean = {k: v for k, v in params.items() if v not in (None, "")}
+        if clean:
+            url += "?" + urllib.parse.urlencode(clean)
+    data = json.dumps(body).encode("utf-8") if body is not None else None
+    headers = {"Authorization": "Bearer " + str(cfg.get("token", "")), "Accept": "application/json"}
+    if data is not None:
+        headers["Content-Type"] = "application/json"
+    req = urllib.request.Request(url, data=data, headers=headers, method=method)
+    with urllib.request.urlopen(req, timeout=60) as r:
+        raw = r.read()
+        return json.loads(raw) if raw else {}
+
+
+def _run(fn):
+    try:
+        print(json.dumps(fn(_cfg(), _inputs())))
+    except urllib.error.HTTPError as e:
+        print(json.dumps({"error": "HTTP " + str(e.code), "detail": e.read().decode("utf-8", "replace")}))
+        sys.exit(1)
+    except Exception as e:
+        print(json.dumps({"error": str(e)}))
+        sys.exit(1)
+
+
+def main(cfg, inputs):
+    team_id = inputs.get("team_id")
+    terms = inputs.get("terms")
+    if not team_id:
+        raise Exception("team_id is required")
+    if not terms:
+        raise Exception("terms is required")
+
+    q = lambda v: urllib.parse.quote(str(v), safe="")
+    return request(
+        "POST",
+        "/teams/" + q(team_id) + "/posts/search",
+        cfg,
+        body={"terms": terms, "is_or_search": True},
+    )
+
+
+_run(main)
diff --git a/integrations/mattermost/scripts/test_connection.py b/integrations/mattermost/scripts/test_connection.py
new file mode 100644
index 0000000..6f2627b
--- /dev/null
+++ b/integrations/mattermost/scripts/test_connection.py
@@ -0,0 +1,44 @@
+import json, os, sys, urllib.parse, urllib.request, urllib.error
+
+
+def _cfg():
+    return json.loads(os.environ.get("INTEGRATION_SECRETS", "{}"))
+
+
+def _inputs():
+    return json.loads(os.environ.get("INTEGRATION_INPUTS", "{}"))
+
+
+def request(method, path, cfg, body=None, params=None):
+    url = str(cfg.get("base_url", "")).rstrip("/") + "/api/v4" + path
+    if params:
+        clean = {k: v for k, v in params.items() if v not in (None, "")}
+        if clean:
+            url += "?" + urllib.parse.urlencode(clean)
+    data = json.dumps(body).encode("utf-8") if body is not None else None
+    headers = {"Authorization": "Bearer " + str(cfg.get("token", "")), "Accept": "application/json"}
+    if data is not None:
+        headers["Content-Type"] = "application/json"
+    req = urllib.request.Request(url, data=data, headers=headers, method=method)
+    with urllib.request.urlopen(req, timeout=60) as r:
+        raw = r.read()
+        return json.loads(raw) if raw else {}
+
+
+def _run(fn):
+    try:
+        print(json.dumps(fn(_cfg(), _inputs())))
+    except urllib.error.HTTPError as e:
+        print(json.dumps({"error": "HTTP " + str(e.code), "detail": e.read().decode("utf-8", "replace")}))
+        sys.exit(1)
+    except Exception as e:
+        print(json.dumps({"error": str(e)}))
+        sys.exit(1)
+
+
+def main(cfg, inputs):
+    resp = request("GET", "/users/me", cfg)
+    return {"ok": True, "user": resp.get("username")}
+
+
+_run(main)