diff --git a/.ci_support/environment.yml b/.ci_support/environment.yml
index 5224c6701..4a659480c 100644
--- a/.ci_support/environment.yml
+++ b/.ci_support/environment.yml
@@ -20,3 +20,4 @@ dependencies:
 - sqsgenerator =0.5.4
 - hatchling =1.29.0
 - hatch-vcs =0.5.0
+- mp-api =0.37.2
diff --git a/pyproject.toml b/pyproject.toml
index 6c9b246a7..4393a326b 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -55,6 +55,10 @@ phonopy = [
     "phonopy==3.3.0",
     "spglib==2.7.0",
 ]
+mp-api = [
+    "mp-api==0.37.2",
+    "pymatgen==2026.3.23",
+]
 
 [tool.ruff]
 exclude = [".ci_support", "tests", "setup.py", "_version.py"]
diff --git a/src/structuretoolkit/build/__init__.py b/src/structuretoolkit/build/__init__.py
index ab11d72b8..180c9df42 100644
--- a/src/structuretoolkit/build/__init__.py
+++ b/src/structuretoolkit/build/__init__.py
@@ -2,6 +2,10 @@
 from structuretoolkit.build.compound import B2, C14, C15, C36, D03
 from structuretoolkit.build.mesh import create_mesh
 from structuretoolkit.build.sqs import sqs_structures
+from structuretoolkit.build.materialsproject import (
+    search as materialsproject_search,
+    by_id as materialsproject_by_id,
+)
 from structuretoolkit.build.surface import (
     get_high_index_surface_info,
     high_index_surface,
@@ -19,4 +23,6 @@
     "sqs_structures",
     "get_high_index_surface_info",
     "high_index_surface",
+    "materialsproject_search",
+    "materialsproject_by_id",
 ]
diff --git a/src/structuretoolkit/build/materialsproject.py b/src/structuretoolkit/build/materialsproject.py
new file mode 100644
index 000000000..742912769
--- /dev/null
+++ b/src/structuretoolkit/build/materialsproject.py
@@ -0,0 +1,138 @@
+from typing import Any, Iterable
+from collections.abc import Generator
+from ase.atoms import Atoms
+from structuretoolkit.common.pymatgen import pymatgen_to_ase
+
+
+def search(
+    chemsys: str | list[str], fields: Iterable[str] = (), api_key=None, **kwargs
+) -> Generator[dict[str, Any], None, None]:
+    """
+    Search the database for all structures matching the given query.
+
+    Note that `chemsys` takes distinct values for unaries, binaries and so!  A query with `chemsys=["Fe", "O"]` will
+    return iron and oxygen structures but not iron oxide.  Similarly `chemsys=["Fe-O"]` will
+    not return unary structures.
+
+    All keyword arguments for filtering from the original API are supported.  See the
+    `original docs <https://docs.materialsproject.org/downloading-data/using-the-api>`_ for them.
+
+    Search for all iron structures:
+
+    >>> irons = structuretoolkit.build.materialsproject.search("Fe")
+    >>> len(list(irons))
+    10
+
+    Search for all structures with Al, Li that are on the T=0 convex hull:
+
+    >>> alli = structuretoolkit.build.materialsproject.search(['Al', 'Li', 'Al-Li'], is_stable=True)
+    >>> len(list(alli))
+    6
+
+    Usage is only possible with an API key obtained from the Materials Project.  To do this, create an account with
+    them, login and access `this webpage <https://next-gen.materialsproject.org/api#api-key>`.
+
+    Once you have a key, either pass it as the `api_key` parameter or export an
+    environment variable, called `MP_API_KEY`, in your shell setup.
+
+    Args:
+        chemsys (str, list of str): confine search to given elements; either an element symbol or multiple element
+            symbols separated by dashes; if a list of strings is given return structures matching either of them
+        fields (iterable of str): pass as `fields` to :meth:`mp_api.MPRester.summary.search` to request additional
+            database entries beyond the structure
+        api_key (str, optional): if your API key is not exported in the environment flag MP_API_KEY, pass it here
+        **kwargs: passed verbatim to :meth:`mp_api.MPRester.summary.search` to further filter the results
+
+    Returns:
+        list of dict: one dictionary for each search results with at least keys
+            'material_id': database key of the hit
+            'structure': ASE atoms object
+            plus any requested via `fields`.
+    """
+    from mp_api.client import MPRester
+
+    rest_kwargs = {
+        "use_document_model": False,  # returns results as dictionaries
+        "include_user_agent": True,  # send some additional software version info to MP
+    }
+    if api_key is not None:
+        rest_kwargs["api_key"] = api_key
+    with MPRester(**rest_kwargs) as mpr:
+        results = mpr.summary.search(
+            chemsys=chemsys,
+            **kwargs,
+            fields=list(fields) + ["structure", "material_id"],
+        )
+    for r in results:
+        if "structure" in r:
+            r["structure"] = pymatgen_to_ase(r["structure"])
+        yield r
+
+
+def by_id(
+    material_id: str | int,
+    final: bool = True,
+    conventional_unit_cell: bool = False,
+    api_key=None,
+) -> Atoms | list[Atoms]:
+    """
+    Retrieve a structure by material id.
+
+    This is how you would ask for the iron ground state:
+
+    >>> structuretoolkit.build.materialsproject.by_id('mp-13')
+    Fe: [0. 0. 0.]
+    tags:
+        spin: [(0: 2.214)]
+    pbc: [ True  True  True]
+    cell:
+    Cell([[2.318956, 0.000185, -0.819712], [-1.159251, 2.008215, -0.819524], [2.5e-05, 0.000273, 2.459206]])
+
+    Usage is only possible with an API key obtained from the Materials Project.  To do this, create an account with
+    them, login and access `this webpage <https://next-gen.materialsproject.org/api#api-key>`.
+
+    Once you have a key, either pass it as the `api_key` parameter or export an
+    environment variable, called `MP_API_KEY`, in your shell setup.
+
+    Args:
+        material_id (str): the id assigned to a structure by the materials project
+        api_key (str, optional): if your API key is not exported in the environment flag MP_API_KEY, pass it here
+        final (bool, optional): if set to False, returns the list of initial structures,
+        else returns the final structure. (Default is True)
+        conventional_unit_cell (bool, optional): if set to True, returns the standard conventional unit cell.
+        (Default is False)
+
+    Returns:
+        :class:`~.Atoms`: requested final structure if final is True
+        list of :class:~.Atoms`:  a list of initial (pre-relaxation) structures if final is False
+
+    Raises:
+        ValueError: material id does not exist
+    """
+    from mp_api.client import MPRester
+
+    rest_kwargs = {
+        "include_user_agent": True,  # send some additional software version info to MP
+    }
+    if api_key is not None:
+        rest_kwargs["api_key"] = api_key
+    with MPRester(**rest_kwargs) as mpr:
+        if final:
+            return pymatgen_to_ase(
+                mpr.get_structure_by_material_id(
+                    material_id=material_id,
+                    final=final,
+                    conventional_unit_cell=conventional_unit_cell,
+                )
+            )
+        else:
+            return [
+                pymatgen_to_ase(mpr_structure)
+                for mpr_structure in (
+                    mpr.get_structure_by_material_id(
+                        material_id=material_id,
+                        final=final,
+                        conventional_unit_cell=conventional_unit_cell,
+                    )
+                )
+            ]
diff --git a/tests/test_materialsproject.py b/tests/test_materialsproject.py
new file mode 100644
index 000000000..7f9bcf1d0
--- /dev/null
+++ b/tests/test_materialsproject.py
@@ -0,0 +1,270 @@
+import importlib
+import unittest
+from unittest.mock import MagicMock, patch
+
+import numpy as np
+from ase.atoms import Atoms
+from ase.build import bulk
+
+from structuretoolkit.build.materialsproject import by_id, search
+
+
+def setUpModule():
+    """Skip the entire module if mp_api and pymatgen are not installed."""
+    if (
+        importlib.util.find_spec("mp_api") is None
+        or importlib.util.find_spec("pymatgen") is None
+    ):
+        raise unittest.SkipTest("mp-api and pymatgen are not installed")
+
+
+def _make_pymatgen_structure(ase_atoms):
+    """Convert ASE Atoms to a pymatgen Structure for use as mock return value."""
+    from pymatgen.io.ase import AseAtomsAdaptor
+
+    return AseAtomsAdaptor().get_structure(atoms=ase_atoms)
+
+
+class TestMaterialsProjectSearch(unittest.TestCase):
+    def setUp(self):
+        self.fe_bcc = bulk("Fe", "bcc", a=2.87)
+        self.al_fcc = bulk("Al", "fcc", a=4.05)
+        self.fe_pmg = _make_pymatgen_structure(self.fe_bcc)
+        self.al_pmg = _make_pymatgen_structure(self.al_fcc)
+
+    def test_search_single_chemsys(self):
+        with patch("mp_api.client.MPRester") as MockMPRester:
+            mock_mpr = MagicMock()
+            MockMPRester.return_value.__enter__ = MagicMock(return_value=mock_mpr)
+            MockMPRester.return_value.__exit__ = MagicMock(return_value=False)
+            mock_mpr.summary.search.return_value = [
+                {"material_id": "mp-13", "structure": self.fe_pmg},
+            ]
+
+            results = list(search("Fe"))
+
+            self.assertEqual(len(results), 1)
+            self.assertEqual(results[0]["material_id"], "mp-13")
+            self.assertIsInstance(results[0]["structure"], Atoms)
+            self.assertEqual(results[0]["structure"].get_chemical_symbols(), ["Fe"])
+
+            mock_mpr.summary.search.assert_called_once_with(
+                chemsys="Fe",
+                fields=["structure", "material_id"],
+            )
+
+    def test_search_multiple_chemsys(self):
+        with patch("mp_api.client.MPRester") as MockMPRester:
+            mock_mpr = MagicMock()
+            MockMPRester.return_value.__enter__ = MagicMock(return_value=mock_mpr)
+            MockMPRester.return_value.__exit__ = MagicMock(return_value=False)
+            mock_mpr.summary.search.return_value = [
+                {"material_id": "mp-13", "structure": self.fe_pmg},
+                {"material_id": "mp-134", "structure": self.al_pmg},
+            ]
+
+            results = list(search(["Fe", "Al"]))
+
+            self.assertEqual(len(results), 2)
+            self.assertEqual(results[0]["material_id"], "mp-13")
+            self.assertEqual(results[1]["material_id"], "mp-134")
+            for r in results:
+                self.assertIsInstance(r["structure"], Atoms)
+
+    def test_search_with_extra_fields(self):
+        with patch("mp_api.client.MPRester") as MockMPRester:
+            mock_mpr = MagicMock()
+            MockMPRester.return_value.__enter__ = MagicMock(return_value=mock_mpr)
+            MockMPRester.return_value.__exit__ = MagicMock(return_value=False)
+            mock_mpr.summary.search.return_value = [
+                {
+                    "material_id": "mp-13",
+                    "structure": self.fe_pmg,
+                    "energy_above_hull": 0.0,
+                },
+            ]
+
+            results = list(search("Fe", fields=["energy_above_hull"]))
+
+            self.assertEqual(results[0]["energy_above_hull"], 0.0)
+            mock_mpr.summary.search.assert_called_once_with(
+                chemsys="Fe",
+                fields=["energy_above_hull", "structure", "material_id"],
+            )
+
+    def test_search_with_kwargs(self):
+        with patch("mp_api.client.MPRester") as MockMPRester:
+            mock_mpr = MagicMock()
+            MockMPRester.return_value.__enter__ = MagicMock(return_value=mock_mpr)
+            MockMPRester.return_value.__exit__ = MagicMock(return_value=False)
+            mock_mpr.summary.search.return_value = [
+                {"material_id": "mp-13", "structure": self.fe_pmg},
+            ]
+
+            list(search("Fe", is_stable=True))
+
+            mock_mpr.summary.search.assert_called_once_with(
+                chemsys="Fe",
+                is_stable=True,
+                fields=["structure", "material_id"],
+            )
+
+    def test_search_with_api_key(self):
+        with patch("mp_api.client.MPRester") as MockMPRester:
+            mock_mpr = MagicMock()
+            MockMPRester.return_value.__enter__ = MagicMock(return_value=mock_mpr)
+            MockMPRester.return_value.__exit__ = MagicMock(return_value=False)
+            mock_mpr.summary.search.return_value = []
+
+            list(search("Fe", api_key="test-key-123"))
+
+            MockMPRester.assert_called_once_with(
+                use_document_model=False,
+                include_user_agent=True,
+                api_key="test-key-123",
+            )
+
+    def test_search_without_api_key(self):
+        with patch("mp_api.client.MPRester") as MockMPRester:
+            mock_mpr = MagicMock()
+            MockMPRester.return_value.__enter__ = MagicMock(return_value=mock_mpr)
+            MockMPRester.return_value.__exit__ = MagicMock(return_value=False)
+            mock_mpr.summary.search.return_value = []
+
+            list(search("Fe"))
+
+            MockMPRester.assert_called_once_with(
+                use_document_model=False,
+                include_user_agent=True,
+            )
+
+    def test_search_empty_results(self):
+        with patch("mp_api.client.MPRester") as MockMPRester:
+            mock_mpr = MagicMock()
+            MockMPRester.return_value.__enter__ = MagicMock(return_value=mock_mpr)
+            MockMPRester.return_value.__exit__ = MagicMock(return_value=False)
+            mock_mpr.summary.search.return_value = []
+
+            results = list(search("Uuo"))
+
+            self.assertEqual(len(results), 0)
+
+    def test_search_is_generator(self):
+        """search() should yield results lazily."""
+        with patch("mp_api.client.MPRester") as MockMPRester:
+            mock_mpr = MagicMock()
+            MockMPRester.return_value.__enter__ = MagicMock(return_value=mock_mpr)
+            MockMPRester.return_value.__exit__ = MagicMock(return_value=False)
+            mock_mpr.summary.search.return_value = [
+                {"material_id": "mp-13", "structure": self.fe_pmg},
+            ]
+
+            gen = search("Fe")
+            import types
+
+            self.assertIsInstance(gen, types.GeneratorType)
+
+
+class TestMaterialsProjectById(unittest.TestCase):
+    def setUp(self):
+        self.fe_bcc = bulk("Fe", "bcc", a=2.87)
+        self.fe_pmg = _make_pymatgen_structure(self.fe_bcc)
+
+    def test_by_id_final(self):
+        with patch("mp_api.client.MPRester") as MockMPRester:
+            mock_mpr = MagicMock()
+            MockMPRester.return_value.__enter__ = MagicMock(return_value=mock_mpr)
+            MockMPRester.return_value.__exit__ = MagicMock(return_value=False)
+            mock_mpr.get_structure_by_material_id.return_value = self.fe_pmg
+
+            result = by_id("mp-13")
+
+            self.assertIsInstance(result, Atoms)
+            self.assertEqual(result.get_chemical_symbols(), ["Fe"])
+            mock_mpr.get_structure_by_material_id.assert_called_once_with(
+                material_id="mp-13",
+                final=True,
+                conventional_unit_cell=False,
+            )
+
+    def test_by_id_not_final(self):
+        with patch("mp_api.client.MPRester") as MockMPRester:
+            mock_mpr = MagicMock()
+            MockMPRester.return_value.__enter__ = MagicMock(return_value=mock_mpr)
+            MockMPRester.return_value.__exit__ = MagicMock(return_value=False)
+            mock_mpr.get_structure_by_material_id.return_value = [
+                self.fe_pmg,
+                self.fe_pmg,
+            ]
+
+            result = by_id("mp-13", final=False)
+
+            self.assertIsInstance(result, list)
+            self.assertEqual(len(result), 2)
+            for atoms in result:
+                self.assertIsInstance(atoms, Atoms)
+            mock_mpr.get_structure_by_material_id.assert_called_once_with(
+                material_id="mp-13",
+                final=False,
+                conventional_unit_cell=False,
+            )
+
+    def test_by_id_conventional_unit_cell(self):
+        with patch("mp_api.client.MPRester") as MockMPRester:
+            mock_mpr = MagicMock()
+            MockMPRester.return_value.__enter__ = MagicMock(return_value=mock_mpr)
+            MockMPRester.return_value.__exit__ = MagicMock(return_value=False)
+            mock_mpr.get_structure_by_material_id.return_value = self.fe_pmg
+
+            by_id("mp-13", conventional_unit_cell=True)
+
+            mock_mpr.get_structure_by_material_id.assert_called_once_with(
+                material_id="mp-13",
+                final=True,
+                conventional_unit_cell=True,
+            )
+
+    def test_by_id_with_api_key(self):
+        with patch("mp_api.client.MPRester") as MockMPRester:
+            mock_mpr = MagicMock()
+            MockMPRester.return_value.__enter__ = MagicMock(return_value=mock_mpr)
+            MockMPRester.return_value.__exit__ = MagicMock(return_value=False)
+            mock_mpr.get_structure_by_material_id.return_value = self.fe_pmg
+
+            by_id("mp-13", api_key="test-key-456")
+
+            MockMPRester.assert_called_once_with(
+                include_user_agent=True,
+                api_key="test-key-456",
+            )
+
+    def test_by_id_without_api_key(self):
+        with patch("mp_api.client.MPRester") as MockMPRester:
+            mock_mpr = MagicMock()
+            MockMPRester.return_value.__enter__ = MagicMock(return_value=mock_mpr)
+            MockMPRester.return_value.__exit__ = MagicMock(return_value=False)
+            mock_mpr.get_structure_by_material_id.return_value = self.fe_pmg
+
+            by_id("mp-13")
+
+            MockMPRester.assert_called_once_with(
+                include_user_agent=True,
+            )
+
+    def test_by_id_structure_has_correct_cell(self):
+        with patch("mp_api.client.MPRester") as MockMPRester:
+            mock_mpr = MagicMock()
+            MockMPRester.return_value.__enter__ = MagicMock(return_value=mock_mpr)
+            MockMPRester.return_value.__exit__ = MagicMock(return_value=False)
+            mock_mpr.get_structure_by_material_id.return_value = self.fe_pmg
+
+            result = by_id("mp-13")
+
+            self.assertTrue(
+                np.allclose(result.cell.array, self.fe_bcc.cell.array, atol=1e-6),
+                "Cell parameters should be preserved through pymatgen conversion.",
+            )
+            self.assertTrue(
+                np.all(result.pbc),
+                "Periodic boundary conditions should be set.",
+            )