diff --git a/Makefile b/Makefile
index 02f3b54..0f4cccd 100644
--- a/Makefile
+++ b/Makefile
@@ -46,9 +46,7 @@ dev: $(VENV)/pyvenv.cfg
 $(VENV)/pyvenv.cfg: pyproject.toml
 	# Create our Python 3 virtual environment
 	python3 -m venv env
-	# NOTE(ekilmer): interrogate v1.5.0 needs setuptools when using Python 3.12+.
-	# This should be fixed when the next release is made
-	$(VENV_BIN)/python -m pip install --upgrade pip setuptools
+	$(VENV_BIN)/python -m pip install --upgrade pip
 	$(VENV_BIN)/python -m pip install -e .[$(INSTALL_EXTRA)]
 
 .PHONY: lint
diff --git a/src/pypi_attestations/__init__.py b/src/pypi_attestations/__init__.py
index 3c43bbd..a57fbae 100644
--- a/src/pypi_attestations/__init__.py
+++ b/src/pypi_attestations/__init__.py
@@ -10,6 +10,8 @@
     ConversionError,
     Distribution,
     Envelope,
+    GitHubPublisher,
+    GitLabPublisher,
     Provenance,
     Publisher,
     TransparencyLogEntry,
@@ -25,6 +27,8 @@
     "ConversionError",
     "Distribution",
     "Envelope",
+    "GitHubPublisher",
+    "GitLabPublisher",
     "Provenance",
     "Publisher",
     "TransparencyLogEntry",
diff --git a/src/pypi_attestations/_impl.py b/src/pypi_attestations/_impl.py
index 021d044..b84d9df 100644
--- a/src/pypi_attestations/_impl.py
+++ b/src/pypi_attestations/_impl.py
@@ -14,7 +14,8 @@
 from cryptography import x509
 from cryptography.hazmat.primitives import serialization
 from packaging.utils import parse_sdist_filename, parse_wheel_filename
-from pydantic import Base64Bytes, BaseModel, field_validator
+from pydantic import Base64Bytes, BaseModel, ConfigDict, Field, field_validator
+from pydantic.alias_generators import to_snake
 from pydantic_core import ValidationError
 from sigstore._utils import _sha256_streaming
 from sigstore.dsse import Envelope as DsseEnvelope
@@ -333,20 +334,58 @@ def _ultranormalize_dist_filename(dist: str) -> str:
         raise ValueError(f"unknown distribution format: {dist}")
 
 
-class Publisher(BaseModel):
-    """Publisher as defined in PEP 740."""
+class _PublisherBase(BaseModel):
+    model_config = ConfigDict(alias_generator=to_snake)
 
     kind: str
+    claims: dict[str, Any] | None = None
+
+
+class GitHubPublisher(_PublisherBase):
+    """A GitHub-based Trusted Publisher."""
+
+    kind: Literal["GitHub"] = "GitHub"
+
+    repository: str
+    """
+    The fully qualified publishing repository slug, e.g. `foo/bar` for
+    repository `bar` owned by `foo`.
+    """
+
+    workflow: str
+    """
+    The filename of the GitHub Actions workflow that performed the publishing
+    action.
+    """
+
+    environment: str | None = None
+    """
+    The optional name GitHub Actions environment that the publishing
+    action was performed from.
     """
-    The kind of Trusted Publisher.
+
+
+class GitLabPublisher(_PublisherBase):
+    """A GitLab-based Trusted Publisher."""
+
+    kind: Literal["GitLab"] = "GitLab"
+
+    repository: str
+    """
+    The fully qualified publishing repository slug, e.g. `foo/bar` for
+    repository `bar` owned by `foo` or `foo/baz/bar` for repository
+    `bar` owned by group `foo` and subgroup `baz`.
     """
 
-    claims: dict[str, Any] | None
+    environment: str | None = None
     """
-    Claims specified by the publisher.
+    The optional environment that the publishing action was performed from.
     """
 
 
+Publisher = Annotated[GitHubPublisher | GitLabPublisher, Field(discriminator="kind")]
+
+
 class AttestationBundle(BaseModel):
     """AttestationBundle object as defined in PEP 740."""
 
@@ -364,7 +403,7 @@ class AttestationBundle(BaseModel):
 class Provenance(BaseModel):
     """Provenance object as defined in PEP 740."""
 
-    version: Literal[1]
+    version: Literal[1] = 1
     """
     The provenance object's version, which is always 1.
     """
@@ -373,12 +412,3 @@ class Provenance(BaseModel):
     """
     One or more attestation "bundles".
     """
-
-    @classmethod
-    def construct_simple(cls, publisher: Publisher, attestations: list[Attestation]) -> Provenance:
-        """Construct a simple Provenance object."""
-        attestation_bundle = AttestationBundle(
-            publisher=publisher,
-            attestations=attestations,
-        )
-        return cls(version=1, attestation_bundles=[attestation_bundle])
diff --git a/test/test_impl.py b/test/test_impl.py
index 84d78ec..5157285 100644
--- a/test/test_impl.py
+++ b/test/test_impl.py
@@ -1,5 +1,6 @@
 """Internal implementation tests."""
 
+import json
 import os
 from hashlib import sha256
 from pathlib import Path
@@ -8,7 +9,7 @@
 import pypi_attestations._impl as impl
 import pytest
 import sigstore
-from pydantic import ValidationError
+from pydantic import TypeAdapter, ValidationError
 from sigstore.dsse import _DigestSet, _StatementBuilder, _Subject
 from sigstore.models import Bundle
 from sigstore.oidc import IdentityToken
@@ -464,17 +465,54 @@ def test_ultranormalize_dist_filename_invalid(input: str) -> None:
         impl._ultranormalize_dist_filename(input)
 
 
-def test_construct_provenance() -> None:
-    attestation = impl.Attestation.model_validate_json(dist_attestation_path.read_bytes())
+class TestPublisher:
+    def test_discriminator(self) -> None:
+        gh_raw = {"kind": "GitHub", "repository": "foo/bar", "workflow": "publish.yml"}
+        gh = TypeAdapter(impl.Publisher).validate_python(gh_raw)
+
+        assert isinstance(gh, impl.GitHubPublisher)
+        assert gh.repository == "foo/bar"
+        assert gh.workflow == "publish.yml"
+        assert TypeAdapter(impl.Publisher).validate_json(json.dumps(gh_raw)) == gh
 
-    publisher = impl.Publisher(kind="simple-publisher-url", claims=None)
-    provenance = impl.Provenance.construct_simple(publisher=publisher, attestations=[attestation])
+        gl_raw = {"kind": "GitLab", "repository": "foo/bar/baz", "environment": "publish"}
+        gl = TypeAdapter(impl.Publisher).validate_python(gl_raw)
+        assert isinstance(gl, impl.GitLabPublisher)
+        assert gl.repository == "foo/bar/baz"
+        assert gl.environment == "publish"
+        assert TypeAdapter(impl.Publisher).validate_json(json.dumps(gl_raw)) == gl
 
-    assert provenance.version == 1
-    assert len(provenance.attestation_bundles) == 1
+    def test_wrong_kind(self) -> None:
+        with pytest.raises(ValueError, match="Input should be 'GitHub'"):
+            impl.GitHubPublisher(kind="wrong", repository="foo/bar", workflow="publish.yml")
 
-    bundle = provenance.attestation_bundles[0]
-    assert bundle.publisher.claims is None
-    assert bundle.publisher.kind == "simple-publisher-url"
+        with pytest.raises(ValueError, match="Input should be 'GitLab'"):
+            impl.GitLabPublisher(kind="GitHub", repository="foo/bar")
 
-    assert bundle.attestations == [attestation]
+
+class TestProvenance:
+    def test_version(self) -> None:
+        attestation = impl.Attestation.model_validate_json(dist_attestation_path.read_bytes())
+        provenance = impl.Provenance(
+            attestation_bundles=[
+                impl.AttestationBundle(
+                    publisher=impl.GitHubPublisher(repository="foo/bar", workflow="publish.yml"),
+                    attestations=[attestation],
+                )
+            ]
+        )
+        assert provenance.version == 1
+
+        # Setting any other version doesn't work.
+        with pytest.raises(ValueError):
+            provenance = impl.Provenance(
+                version=2,
+                attestation_bundles=[
+                    impl.AttestationBundle(
+                        publisher=impl.GitHubPublisher(
+                            repository="foo/bar", workflow="publish.yml"
+                        ),
+                        attestations=[attestation],
+                    )
+                ],
+            )