diff --git a/CHANGELOG.md b/CHANGELOG.md
index bd05fb064..85e232215 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,7 @@
 - `sort_links_by_id` to Catalog `get_child()` and `modify_links` to `get_stac_objects()` ([#1064](https://github.com/stac-utils/pystac/pull/1064))
 - `*ids` to Catalog and Collection `get_items()` for only including the provided ids in the iterator ([#1075](https://github.com/stac-utils/pystac/pull/1075))
 - `recursive` to Catalog and Collection `get_items()` to walk the sub-catalogs and sub-collections ([#1075](https://github.com/stac-utils/pystac/pull/1075))
+- MGRS Extension ([#1088](https://github.com/stac-utils/pystac/pull/1088))
 
 ### Changed
 
diff --git a/docs/api.rst b/docs/api.rst
index c1e1a84dc..604000928 100644
--- a/docs/api.rst
+++ b/docs/api.rst
@@ -96,6 +96,7 @@ PySTAC provides support for the following STAC Extensions:
 * :mod:`File Info <pystac.extensions.file>`
 * :mod:`Item Assets <pystac.extensions.item_assets>`
 * :mod:`Label <pystac.extensions.label>`
+* :mod:`MGRS <pystac.extensions.mgrs>`
 * :mod:`Point Cloud <pystac.extensions.pointcloud>`
 * :mod:`Projection <pystac.extensions.projection>`
 * :mod:`Raster <pystac.extensions.raster>`
diff --git a/docs/api/extensions/mgrs.rst b/docs/api/extensions/mgrs.rst
new file mode 100644
index 000000000..880f8525d
--- /dev/null
+++ b/docs/api/extensions/mgrs.rst
@@ -0,0 +1,7 @@
+pystac.extensions.mgrs
+============================
+
+.. automodule:: pystac.extensions.mgrs
+   :members:
+   :undoc-members:
+   :show-inheritance:
diff --git a/pystac/__init__.py b/pystac/__init__.py
index 68350f909..c3da1a9ee 100644
--- a/pystac/__init__.py
+++ b/pystac/__init__.py
@@ -89,6 +89,7 @@
 import pystac.extensions.file
 import pystac.extensions.item_assets
 import pystac.extensions.label
+import pystac.extensions.mgrs
 import pystac.extensions.pointcloud
 import pystac.extensions.projection
 import pystac.extensions.sar
@@ -107,6 +108,7 @@
         pystac.extensions.file.FILE_EXTENSION_HOOKS,
         pystac.extensions.item_assets.ITEM_ASSETS_EXTENSION_HOOKS,
         pystac.extensions.label.LABEL_EXTENSION_HOOKS,
+        pystac.extensions.mgrs.MGRS_EXTENSION_HOOKS,
         pystac.extensions.pointcloud.POINTCLOUD_EXTENSION_HOOKS,
         pystac.extensions.projection.PROJECTION_EXTENSION_HOOKS,
         pystac.extensions.sar.SAR_EXTENSION_HOOKS,
diff --git a/pystac/extensions/mgrs.py b/pystac/extensions/mgrs.py
new file mode 100644
index 000000000..5e3cc7beb
--- /dev/null
+++ b/pystac/extensions/mgrs.py
@@ -0,0 +1,249 @@
+"""Implements the :stac-ext:`MGRS Extension <mgrs>`."""
+
+import re
+from typing import Any, Dict, FrozenSet, Optional, Pattern, Set, Union
+
+import pystac
+from pystac.extensions.base import ExtensionManagementMixin, PropertiesExtension
+from pystac.extensions.hooks import ExtensionHooks
+
+SCHEMA_URI: str = "https://stac-extensions.github.io/mgrs/v1.0.0/schema.json"
+PREFIX: str = "mgrs:"
+
+# Field names
+LATITUDE_BAND_PROP: str = PREFIX + "latitude_band"  # required
+GRID_SQUARE_PROP: str = PREFIX + "grid_square"  # required
+UTM_ZONE_PROP: str = PREFIX + "utm_zone"
+
+LATITUDE_BANDS: FrozenSet[str] = frozenset(
+    {
+        "C",
+        "D",
+        "E",
+        "F",
+        "G",
+        "H",
+        "J",
+        "K",
+        "L",
+        "M",
+        "N",
+        "P",
+        "Q",
+        "R",
+        "S",
+        "T",
+        "U",
+        "V",
+        "W",
+        "X",
+    }
+)
+
+UTM_ZONES: FrozenSet[int] = frozenset(
+    {
+        1,
+        2,
+        3,
+        4,
+        5,
+        6,
+        7,
+        8,
+        9,
+        10,
+        11,
+        12,
+        13,
+        14,
+        15,
+        16,
+        17,
+        18,
+        19,
+        20,
+        21,
+        22,
+        23,
+        24,
+        25,
+        26,
+        27,
+        28,
+        29,
+        30,
+        31,
+        32,
+        33,
+        34,
+        35,
+        36,
+        37,
+        38,
+        39,
+        40,
+        41,
+        42,
+        43,
+        44,
+        45,
+        46,
+        47,
+        48,
+        49,
+        50,
+        51,
+        52,
+        53,
+        54,
+        55,
+        56,
+        57,
+        58,
+        59,
+        60,
+    }
+)
+
+GRID_SQUARE_REGEX: str = (
+    r"[ABCDEFGHJKLMNPQRSTUVWXYZ][ABCDEFGHJKLMNPQRSTUV](\d{2}|\d{4}|\d{6}|\d{8}|\d{10})?"
+)
+GRID_SQUARE_PATTERN: Pattern[str] = re.compile(GRID_SQUARE_REGEX)
+
+
+def validated_latitude_band(v: str) -> str:
+    if not isinstance(v, str):
+        raise ValueError("Invalid MGRS latitude band: must be str")
+    if v not in LATITUDE_BANDS:
+        raise ValueError(f"Invalid MGRS latitude band: {v} is not in {LATITUDE_BANDS}")
+    return v
+
+
+def validated_grid_square(v: str) -> str:
+    if not isinstance(v, str):
+        raise ValueError("Invalid MGRS grid square identifier: must be str")
+    if not GRID_SQUARE_PATTERN.fullmatch(v):
+        raise ValueError(
+            f"Invalid MGRS grid square identifier: {v}"
+            f" does not match the regex {GRID_SQUARE_REGEX}"
+        )
+    return v
+
+
+def validated_utm_zone(v: Optional[int]) -> Optional[int]:
+    if v is not None and not isinstance(v, int):
+        raise ValueError("Invalid MGRS utm zone: must be None or int")
+    if v is not None and v not in UTM_ZONES:
+        raise ValueError(f"Invalid MGRS UTM zone: {v} is not in {UTM_ZONES}")
+    return v
+
+
+class MgrsExtension(
+    PropertiesExtension,
+    ExtensionManagementMixin[Union[pystac.Item, pystac.Collection]],
+):
+    """A concrete implementation of :class:`MgrsExtension` on an :class:`~pystac.Item`
+    that extends the properties of the Item to include properties defined in the
+    :stac-ext:`MGRS Extension <mgrs>`.
+
+    This class should generally not be instantiated directly. Instead, call
+    :meth:`MgrsExtension.ext` on an :class:`~pystac.Item` to extend it.
+
+    .. code-block:: python
+
+       >>> item: pystac.Item = ...
+       >>> proj_ext = MgrsExtension.ext(item)
+    """
+
+    item: pystac.Item
+    """The :class:`~pystac.Item` being extended."""
+
+    properties: Dict[str, Any]
+    """The :class:`~pystac.Item` properties, including extension properties."""
+
+    def __init__(self, item: pystac.Item):
+        self.item = item
+        self.properties = item.properties
+
+    def __repr__(self) -> str:
+        return "<ItemMgrsExtension Item id={}>".format(self.item.id)
+
+    def apply(
+        self,
+        latitude_band: str,
+        grid_square: str,
+        utm_zone: Optional[int] = None,
+    ) -> None:
+        """Applies MGRS extension properties to the extended Item.
+
+        Args:
+            latitude_band : REQUIRED. The latitude band of the Item's centroid.
+            grid_square : REQUIRED. MGRS grid square of the Item's centroid.
+            utm_zone : The UTM Zone of the Item centroid.
+        """
+        self.latitude_band = validated_latitude_band(latitude_band)
+        self.grid_square = validated_grid_square(grid_square)
+        self.utm_zone = validated_utm_zone(utm_zone)
+
+    @property
+    def latitude_band(self) -> Optional[str]:
+        """Get or sets the latitude band of the datasource."""
+        return self._get_property(LATITUDE_BAND_PROP, str)
+
+    @latitude_band.setter
+    def latitude_band(self, v: str) -> None:
+        self._set_property(
+            LATITUDE_BAND_PROP, validated_latitude_band(v), pop_if_none=False
+        )
+
+    @property
+    def grid_square(self) -> Optional[str]:
+        """Get or sets the latitude band of the datasource."""
+        return self._get_property(GRID_SQUARE_PROP, str)
+
+    @grid_square.setter
+    def grid_square(self, v: str) -> None:
+        self._set_property(
+            GRID_SQUARE_PROP, validated_grid_square(v), pop_if_none=False
+        )
+
+    @property
+    def utm_zone(self) -> Optional[int]:
+        """Get or sets the latitude band of the datasource."""
+        return self._get_property(UTM_ZONE_PROP, int)
+
+    @utm_zone.setter
+    def utm_zone(self, v: Optional[int]) -> None:
+        self._set_property(UTM_ZONE_PROP, validated_utm_zone(v), pop_if_none=True)
+
+    @classmethod
+    def get_schema_uri(cls) -> str:
+        return SCHEMA_URI
+
+    @classmethod
+    def ext(cls, obj: pystac.Item, add_if_missing: bool = False) -> "MgrsExtension":
+        """Extends the given STAC Object with properties from the :stac-ext:`MGRS
+        Extension <mgrs>`.
+
+        This extension can be applied to instances of :class:`~pystac.Item`.
+
+        Raises:
+
+            pystac.ExtensionTypeError : If an invalid object type is passed.
+        """
+        if isinstance(obj, pystac.Item):
+            cls.validate_has_extension(obj, add_if_missing)
+            return MgrsExtension(obj)
+        else:
+            raise pystac.ExtensionTypeError(
+                f"MGRS Extension does not apply to type '{type(obj).__name__}'"
+            )
+
+
+class MgrsExtensionHooks(ExtensionHooks):
+    schema_uri: str = SCHEMA_URI
+    prev_extension_ids: Set[str] = set()
+    stac_object_types = {pystac.STACObjectType.ITEM}
+
+
+MGRS_EXTENSION_HOOKS: ExtensionHooks = MgrsExtensionHooks()
diff --git a/tests/conftest.py b/tests/conftest.py
index d449add98..95531df2a 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -1,5 +1,6 @@
 # TODO move all test case code to this file
 
+from pathlib import Path
 from datetime import datetime
 
 import pytest
@@ -9,6 +10,9 @@
 from .utils import ARBITRARY_BBOX, ARBITRARY_EXTENT, ARBITRARY_GEOM, TestCases
 
 
+here = Path(__file__).resolve().parent
+
+
 @pytest.fixture
 def catalog() -> Catalog:
     return Catalog("test-catalog", "A test catalog")
@@ -38,3 +42,7 @@ def test_case_8_collection() -> Collection:
 def projection_landsat8_item() -> Item:
     path = TestCases.get_path("data-files/projection/example-landsat8.json")
     return Item.from_file(path)
+
+
+def get_data_file(rel_path: str) -> str:
+    return str(here / "data-files" / rel_path)
diff --git a/tests/data-files/mgrs/item.json b/tests/data-files/mgrs/item.json
new file mode 100644
index 000000000..97a56b19b
--- /dev/null
+++ b/tests/data-files/mgrs/item.json
@@ -0,0 +1,53 @@
+{
+  "stac_version": "1.0.0",
+  "stac_extensions": [
+    "https://stac-extensions.github.io/mgrs/v1.0.0/schema.json"
+  ],
+  "type": "Feature",
+  "id": "item",
+  "bbox": [
+    172.9,
+    1.3,
+    173,
+    1.4
+  ],
+  "geometry": {
+    "type": "Polygon",
+    "coordinates": [
+      [
+        [
+          172.9,
+          1.3
+        ],
+        [
+          173,
+          1.3
+        ],
+        [
+          173,
+          1.4
+        ],
+        [
+          172.9,
+          1.4
+        ],
+        [
+          172.9,
+          1.3
+        ]
+      ]
+    ]
+  },
+  "properties": {
+    "datetime": "2020-12-11T22:38:32Z",
+    "mgrs:utm_zone": 13,
+    "mgrs:latitude_band": "X",
+    "mgrs:grid_square": "DH"
+  },
+  "links": [],
+  "assets": {
+    "data": {
+      "href": "https://example.com/examples/file.xyz"
+    }
+  }
+}
\ No newline at end of file
diff --git a/tests/extensions/test_mgrs.py b/tests/extensions/test_mgrs.py
new file mode 100644
index 000000000..5e8b03c99
--- /dev/null
+++ b/tests/extensions/test_mgrs.py
@@ -0,0 +1,126 @@
+"""Tests for pystac.tests.extensions.mgrs"""
+import json
+import pytest
+import pystac
+from pystac.extensions.mgrs import MgrsExtension
+
+
+from tests.conftest import get_data_file
+
+
+@pytest.fixture
+def ext_item_uri() -> str:
+    return get_data_file("mgrs/item.json")
+
+
+@pytest.fixture
+def ext_item(ext_item_uri: str) -> pystac.Item:
+    return pystac.Item.from_file(ext_item_uri)
+
+
+def test_stac_extensions(ext_item: pystac.Item) -> None:
+    assert MgrsExtension.has_extension(ext_item)
+
+
+def test_get_schema_uri(ext_item: pystac.Item) -> None:
+    assert MgrsExtension.get_schema_uri() in ext_item.stac_extensions
+
+
+def test_ext_raises_if_item_does_not_conform(item: pystac.Item) -> None:
+    with pytest.raises(pystac.errors.ExtensionNotImplemented):
+        MgrsExtension.ext(item)
+
+
+def test_to_from_dict(ext_item_uri: str, ext_item: pystac.Item) -> None:
+    with open(ext_item_uri) as f:
+        d = json.load(f)
+    actual = ext_item.to_dict(include_self_link=False)
+    assert actual == d
+
+
+def test_add_to(item: pystac.Item) -> None:
+    assert not MgrsExtension.has_extension(item)
+    MgrsExtension.add_to(item)
+
+    assert MgrsExtension.has_extension(item)
+
+
+def test_apply(item: pystac.Item) -> None:
+    MgrsExtension.add_to(item)
+    MgrsExtension.ext(item).apply(latitude_band="X", grid_square="DH")
+    assert MgrsExtension.ext(item).latitude_band
+    assert MgrsExtension.ext(item).grid_square
+
+
+def test_apply_without_required_fields_raises(item: pystac.Item) -> None:
+    MgrsExtension.add_to(item)
+    with pytest.raises(TypeError, match="missing 2 required positional arguments"):
+        MgrsExtension.ext(item).apply()  # type: ignore
+
+
+def test_validate(ext_item: pystac.Item) -> None:
+    assert ext_item.validate()
+
+
+@pytest.mark.parametrize("field", ["latitude_band", "grid_square", "utm_zone"])
+def test_get_field(ext_item: pystac.Item, field: str) -> None:
+    prop = ext_item.properties[f"mgrs:{field}"]
+    attr = getattr(MgrsExtension.ext(ext_item), field)
+
+    assert attr is not None
+    assert attr == prop
+
+
+@pytest.mark.parametrize(
+    "field,value",
+    [
+        ("latitude_band", "C"),
+        ("grid_square", "ZA"),
+        ("utm_zone", 59),
+    ],
+)
+def test_set_field(ext_item: pystac.Item, field: str, value) -> None:  # type: ignore
+    original = ext_item.properties[f"mgrs:{field}"]
+    setattr(MgrsExtension.ext(ext_item), field, value)
+    new = ext_item.properties[f"mgrs:{field}"]
+
+    assert new != original
+    assert new == value
+    assert ext_item.validate()
+
+
+def test_utm_zone_set_to_none_pops_from_dict(ext_item: pystac.Item) -> None:
+    assert "mgrs:utm_zone" in ext_item.properties
+
+    MgrsExtension.ext(ext_item).utm_zone = None
+    assert "mgrs:utm_zone" not in ext_item.properties
+
+
+def test_invalid_latitude_band_raises_informative_error(ext_item: pystac.Item) -> None:
+    with pytest.raises(ValueError, match="must be str"):
+        MgrsExtension.ext(ext_item).latitude_band = 2  # type: ignore
+
+    with pytest.raises(ValueError, match="must be str"):
+        MgrsExtension.ext(ext_item).latitude_band = None
+
+    with pytest.raises(ValueError, match="a is not in "):
+        MgrsExtension.ext(ext_item).latitude_band = "a"
+
+
+def test_invalid_grid_square_raises_informative_error(ext_item: pystac.Item) -> None:
+    with pytest.raises(ValueError, match="must be str"):
+        MgrsExtension.ext(ext_item).grid_square = 2  # type: ignore
+
+    with pytest.raises(ValueError, match="must be str"):
+        MgrsExtension.ext(ext_item).grid_square = None
+
+    with pytest.raises(ValueError, match="nv does not match the regex "):
+        MgrsExtension.ext(ext_item).grid_square = "nv"
+
+
+def test_invalid_utm_zone_raises_informative_error(ext_item: pystac.Item) -> None:
+    with pytest.raises(ValueError, match="must be None or int"):
+        MgrsExtension.ext(ext_item).utm_zone = "foo"  # type: ignore
+
+    with pytest.raises(ValueError, match="61 is not in "):
+        MgrsExtension.ext(ext_item).utm_zone = 61