diff --git a/docs/configuration.md b/docs/configuration.md
index f1fac414dbe..73450c204a4 100644
--- a/docs/configuration.md
+++ b/docs/configuration.md
@@ -119,6 +119,15 @@ This also works for secret settings, like credentials:
 export POETRY_HTTP_BASIC_MY_REPOSITORY_PASSWORD=secret
 ```
 
+### Add caller data to the User-Agent
+
+Set `POETRY_USER_AGENT_USER_DATA` to append caller-provided context to the
+User-Agent on requests made by Poetry, including package downloads and uploads:
+
+```bash
+export POETRY_USER_AGENT_USER_DATA=build/42
+```
+
 ## Configuration sources
 
 When a setting is set in multiple places, Poetry applies the following precedence
diff --git a/src/poetry/publishing/uploader.py b/src/poetry/publishing/uploader.py
index edc67e40080..b055baba6af 100644
--- a/src/poetry/publishing/uploader.py
+++ b/src/poetry/publishing/uploader.py
@@ -17,14 +17,13 @@
 from packaging.metadata import parse_email
 from poetry.core.constraints.version import Version
 from poetry.core.masonry.utils.helpers import distribution_name
-from requests_toolbelt import user_agent
 from requests_toolbelt.multipart import MultipartEncoder
 from requests_toolbelt.multipart import MultipartEncoderMonitor
 
-from poetry.__version__ import __version__
 from poetry.publishing.hash_manager import HashManager
 from poetry.utils.constants import REQUESTS_TIMEOUT
 from poetry.utils.patterns import wheel_file_re
+from poetry.utils.user_agent import get_user_agent
 
 
 if TYPE_CHECKING:
@@ -48,8 +47,7 @@ def __init__(self, poetry: Poetry, io: IO, dist_dir: Path | None = None) -> None
 
     @property
     def user_agent(self) -> str:
-        agent: str = user_agent("poetry", __version__)
-        return agent
+        return get_user_agent()
 
     @property
     def default_dist_dir(self) -> Path:
diff --git a/src/poetry/utils/authenticator.py b/src/poetry/utils/authenticator.py
index 4c23be1849c..741793f4c61 100644
--- a/src/poetry/utils/authenticator.py
+++ b/src/poetry/utils/authenticator.py
@@ -18,9 +18,7 @@
 
 from cachecontrol import CacheControlAdapter
 from cachecontrol.caches import SeparateBodyFileCache
-from requests_toolbelt import user_agent
 
-from poetry.__version__ import __version__
 from poetry.config.config import Config
 from poetry.console.exceptions import ConsoleMessage
 from poetry.console.exceptions import PoetryRuntimeError
@@ -30,6 +28,7 @@
 from poetry.utils.constants import STATUS_FORCELIST
 from poetry.utils.password_manager import HTTPAuthCredential
 from poetry.utils.password_manager import PasswordManager
+from poetry.utils.user_agent import get_user_agent
 
 
 if TYPE_CHECKING:
@@ -133,7 +132,7 @@ def __init__(
             self._get_repository_config_for_url
         )
         self._pool_size = pool_size
-        self._user_agent = user_agent("poetry", __version__)
+        self._user_agent = get_user_agent()
 
     def create_session(self) -> requests.Session:
         session = requests.Session()
diff --git a/src/poetry/utils/user_agent.py b/src/poetry/utils/user_agent.py
new file mode 100644
index 00000000000..8b071311fdc
--- /dev/null
+++ b/src/poetry/utils/user_agent.py
@@ -0,0 +1,17 @@
+from __future__ import annotations
+
+import os
+
+from requests_toolbelt import user_agent as requests_user_agent
+
+from poetry.__version__ import __version__
+
+
+def get_user_agent() -> str:
+    """Build Poetry's User-Agent, including optional caller context."""
+    extras: list[tuple[str, str]] = []
+    user_data = os.environ.get("POETRY_USER_AGENT_USER_DATA")
+    if user_data is not None:
+        extras.append(("user_data", user_data))
+
+    return str(requests_user_agent("poetry", __version__, extras=extras))
diff --git a/tests/publishing/test_uploader.py b/tests/publishing/test_uploader.py
index eb694bdd035..930171493db 100644
--- a/tests/publishing/test_uploader.py
+++ b/tests/publishing/test_uploader.py
@@ -18,6 +18,7 @@
 
     import responses
 
+    from pytest import MonkeyPatch
     from pytest_mock import MockerFixture
 
     from poetry.poetry import Poetry
@@ -34,6 +35,14 @@ def uploader(poetry: Poetry) -> Uploader:
     return Uploader(poetry, NullIO())
 
 
+def test_user_agent_includes_user_data(
+    uploader: Uploader, monkeypatch: MonkeyPatch
+) -> None:
+    monkeypatch.setenv("POETRY_USER_AGENT_USER_DATA", "build/42")
+
+    assert "user_data/build/42" in uploader.user_agent
+
+
 @pytest.mark.parametrize(
     ("files", "expected_files", "expected_version"),
     [
diff --git a/tests/utils/test_authenticator.py b/tests/utils/test_authenticator.py
index 3fe048b518f..5a309663dee 100644
--- a/tests/utils/test_authenticator.py
+++ b/tests/utils/test_authenticator.py
@@ -134,6 +134,14 @@ def test_authenticator_ignores_failing_keyring(
     assert spy_get_credential.call_count == spy_get_password.call_count == 0
 
 
+def test_authenticator_user_agent_includes_user_data(monkeypatch: MonkeyPatch) -> None:
+    monkeypatch.setenv("POETRY_USER_AGENT_USER_DATA", "build/42")
+
+    authenticator = Authenticator(disable_cache=True)
+
+    assert "user_data/build/42" in authenticator.create_session().headers["User-Agent"]
+
+
 def test_authenticator_uses_password_only_credentials(
     mock_config: Config, mock_remote: None, http: responses.RequestsMock
 ) -> None: