diff --git a/.github/workflows/codspeed.yml b/.github/workflows/codspeed.yml
new file mode 100644
index 0000000..1dd34dd
--- /dev/null
+++ b/.github/workflows/codspeed.yml
@@ -0,0 +1,41 @@
+name: CodSpeed
+
+permissions: {}
+
+on:
+  workflow_dispatch:
+  pull_request:
+  push:
+    branches:
+      - main
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+env:
+  FORCE_COLOR: 3
+
+jobs:
+  benchmarks:
+    name: Run benchmarks
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      id-token: write # for OpenID Connect authentication with CodSpeed
+    steps:
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+
+      - name: Install uv
+        uses: astral-sh/setup-uv@cec208311dfd045dd5311c1add060b2062131d57 # v8.0.0
+        with:
+          python-version: "3.13"
+
+      - name: Install
+        run: uv sync --no-default-groups --group test --locked
+
+      - name: Run benchmarks
+        uses: CodSpeedHQ/action@9a94d4f4af407c62dfa28ecf6a32e8e914cef4cf # v4.18.5
+        with:
+          mode: simulation
+          run: uv run --frozen pytest benchmarks/ --codspeed -p no:sybil
diff --git a/README.md b/README.md
index f9c69e2..993079e 100644
--- a/README.md
+++ b/README.md
@@ -9,6 +9,7 @@
 <p align="center">
     <a href="https://github.com/GalacticDynamics/dataclassish/actions"> <img alt="CI status" src="https://github.com/GalacticDynamics/dataclassish/workflows/CI/badge.svg" /> </a>
     <a href="https://codecov.io/gh/GalacticDynamics/dataclassish"> <img alt="codecov" src="https://codecov.io/gh/GalacticDynamics/dataclassish/graph/badge.svg" /> </a>
+    <a href="https://app.codspeed.io/GalacticDynamics/dataclassish?utm_source=badge"><img alt="CodSpeed" src="https://img.shields.io/endpoint?url=https://codspeed.io/badge.json" /> </a>
     <a href="https://scientific-python.org/specs/spec-0000/"> <img alt="ruff" src="https://img.shields.io/badge/SPEC-0-green?labelColor=%23004811&color=%235CA038" /> </a>
     <a href="https://docs.astral.sh/ruff/"> <img alt="ruff" src="https://img.shields.io/endpoint?url=https://raw.githubusercontent.com/charliermarsh/ruff/main/assets/badge/v2.json" /> </a>
     <a href="https://pre-commit.com"> <img alt="pre-commit" src="https://img.shields.io/badge/pre--commit-enabled-brightgreen?logo=pre-commit" /> </a>
diff --git a/benchmarks/__init__.py b/benchmarks/__init__.py
new file mode 100644
index 0000000..87c8fea
--- /dev/null
+++ b/benchmarks/__init__.py
@@ -0,0 +1 @@
+"""Performance benchmarks for `dataclassish`."""
diff --git a/benchmarks/test_benchmarks.py b/benchmarks/test_benchmarks.py
new file mode 100644
index 0000000..d3a3933
--- /dev/null
+++ b/benchmarks/test_benchmarks.py
@@ -0,0 +1,145 @@
+"""Benchmarks for `dataclassish`.
+
+These benchmarks exercise the public, multiple-dispatch-based API of
+``dataclassish`` across the different object types it supports (mappings and
+dataclasses). They are collected and run by ``pytest-codspeed``.
+"""
+
+from dataclasses import dataclass
+
+import pytest
+
+from dataclassish import (
+    asdict,
+    astuple,
+    field_items,
+    field_keys,
+    field_values,
+    fields,
+    get_field,
+    replace,
+)
+from dataclassish.converters import (
+    Optional,
+    Unless,
+    dataclass as converter_dataclass,
+    field as converter_field,
+)
+
+
+@dataclass(frozen=True)
+class Point:
+    """A small dataclass used across the benchmarks."""
+
+    x: int
+    y: int
+    z: int
+
+
+def _make_mapping() -> dict[str, object]:
+    return {"a": 1, "b": 2.0, "c": "3", "d": 4, "e": 5.0}
+
+
+def _make_point() -> Point:
+    return Point(1, 2, 3)
+
+
+# ============================================================================
+# Mapping dispatches
+
+
+@pytest.mark.benchmark
+def test_replace_mapping(benchmark: object) -> None:
+    """Benchmark `replace` on a mapping."""
+    d = _make_mapping()
+    benchmark(lambda: replace(d, c=3 + 0j, d=40))
+
+
+@pytest.mark.benchmark
+def test_asdict_mapping(benchmark: object) -> None:
+    """Benchmark `asdict` on a mapping."""
+    d = _make_mapping()
+    benchmark(lambda: asdict(d))
+
+
+@pytest.mark.benchmark
+def test_field_items_mapping(benchmark: object) -> None:
+    """Benchmark `field_items` on a mapping."""
+    d = _make_mapping()
+    benchmark(lambda: field_items(d))
+
+
+# ============================================================================
+# Dataclass dispatches
+
+
+@pytest.mark.benchmark
+def test_replace_dataclass(benchmark: object) -> None:
+    """Benchmark `replace` on a dataclass."""
+    p = _make_point()
+    benchmark(lambda: replace(p, x=10, z=30))
+
+
+@pytest.mark.benchmark
+def test_fields_dataclass(benchmark: object) -> None:
+    """Benchmark `fields` on a dataclass."""
+    p = _make_point()
+    benchmark(lambda: fields(p))
+
+
+@pytest.mark.benchmark
+def test_asdict_dataclass(benchmark: object) -> None:
+    """Benchmark `asdict` on a dataclass."""
+    p = _make_point()
+    benchmark(lambda: asdict(p))
+
+
+@pytest.mark.benchmark
+def test_astuple_dataclass(benchmark: object) -> None:
+    """Benchmark `astuple` on a dataclass."""
+    p = _make_point()
+    benchmark(lambda: astuple(p))
+
+
+@pytest.mark.benchmark
+def test_get_field_dataclass(benchmark: object) -> None:
+    """Benchmark `get_field` on a dataclass."""
+    p = _make_point()
+    benchmark(lambda: get_field(p, "y"))
+
+
+@pytest.mark.benchmark
+def test_field_keys_dataclass(benchmark: object) -> None:
+    """Benchmark `field_keys` on a dataclass."""
+    p = _make_point()
+    benchmark(lambda: field_keys(p))
+
+
+@pytest.mark.benchmark
+def test_field_values_dataclass(benchmark: object) -> None:
+    """Benchmark `field_values` on a dataclass."""
+    p = _make_point()
+    benchmark(lambda: field_values(p))
+
+
+@pytest.mark.benchmark
+def test_field_items_dataclass(benchmark: object) -> None:
+    """Benchmark `field_items` on a dataclass."""
+    p = _make_point()
+    benchmark(lambda: field_items(p))
+
+
+# ============================================================================
+# Converters
+
+
+@pytest.mark.benchmark
+def test_converter_dataclass_construction(benchmark: object) -> None:
+    """Benchmark constructing a converter-enabled dataclass."""
+
+    @converter_dataclass(frozen=True, slots=True)
+    class Model:
+        a: int | None = converter_field(converter=Optional(int))
+        b: float = converter_field(converter=Unless(float, float))
+
+    benchmark(lambda: Model(a="1", b=2))
diff --git a/pyproject.toml b/pyproject.toml
index 757372d..0c7548a 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -55,6 +55,7 @@ nox = ["nox>=2024.10.9", "nox-uv>=0.6.3"]
 test = [
   "attrs>=25.4.0",
   "pytest>=8.4.2",
+  "pytest-codspeed>=5.0.0",
   "pytest-cov>=7.0.0",
   "sybil[pytest]>=9.2.0",
 ]
diff --git a/uv.lock b/uv.lock
index 9d0cde4..7ce765e 100644
--- a/uv.lock
+++ b/uv.lock
@@ -289,6 +289,7 @@ dev = [
     { name = "pre-commit" },
     { name = "pylint" },
     { name = "pytest" },
+    { name = "pytest-codspeed" },
     { name = "pytest-cov" },
     { name = "sybil", extra = ["pytest"] },
 ]
@@ -304,6 +305,7 @@ nox = [
 test = [
     { name = "attrs" },
     { name = "pytest" },
+    { name = "pytest-codspeed" },
     { name = "pytest-cov" },
     { name = "sybil", extra = ["pytest"] },
 ]
@@ -327,6 +329,7 @@ dev = [
     { name = "pre-commit", specifier = ">=4.5.0" },
     { name = "pylint", specifier = ">=4.0.4" },
     { name = "pytest", specifier = ">=8.4.2" },
+    { name = "pytest-codspeed", specifier = ">=5.0.0" },
     { name = "pytest-cov", specifier = ">=7.0.0" },
     { name = "sybil", extras = ["pytest"], specifier = ">=9.2.0" },
 ]
@@ -342,6 +345,7 @@ nox = [
 test = [
     { name = "attrs", specifier = ">=25.4.0" },
     { name = "pytest", specifier = ">=8.4.2" },
+    { name = "pytest-codspeed", specifier = ">=5.0.0" },
     { name = "pytest-cov", specifier = ">=7.0.0" },
     { name = "sybil", extras = ["pytest"], specifier = ">=9.2.0" },
 ]
@@ -812,6 +816,40 @@ wheels = [
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 ]
 
+[[package]]
+name = "pytest-codspeed"
+version = "5.0.3"
+source = { registry = "https://pypi.org/simple" }
+dependencies = [
+    { name = "pytest" },
+    { name = "rich" },
+]
+sdist = { url = "https://files.pythonhosted.org/packages/e1/b4/cf932fcd1960a2fd6d9b09eb403253a8709aeee975961afa6299239a830e/pytest_codspeed-5.0.3.tar.gz", hash = "sha256:91afef90e6a96b013495e4702ef5d6358614a449e71008cdc194ef668778b92f", size = 324571, upload-time = "2026-05-22T16:20:49.231Z" }
+wheels = [
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+    { url = "https://files.pythonhosted.org/packages/2a/15/c66ef90a793c5d2c039e63a1726a5e55c678be2618b0f5f1660d0f79e25f/pytest_codspeed-5.0.3-cp311-cp311-manylinux2014_aarch64.manylinux_2_17_aarch64.manylinux_2_28_aarch64.whl", hash = "sha256:4c682f6645d4eb472f3bd95dbda1805e3af4243610572cb7d6bf94a88e8a0b6c", size = 932465, upload-time = "2026-05-22T16:20:34.265Z" },
+    { url = "https://files.pythonhosted.org/packages/1a/7b/d231279301967f05b7909160489e85ee3a1b9da76094ea25343faba1abc2/pytest_codspeed-5.0.3-cp311-cp311-manylinux2014_x86_64.manylinux_2_17_x86_64.manylinux_2_28_x86_64.whl", hash = "sha256:f852bee785a7a124cb1720b1915670c6742af87747dc4d838f3ffdbd365ce9d9", size = 934925, upload-time = "2026-05-22T16:20:47.63Z" },
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+]
+
 [[package]]
 name = "pytest-cov"
 version = "7.0.0"