diff --git a/homeassistant/const.py b/homeassistant/const.py
index ec8c29de0b7ab..a6aa5eac06819 100644
--- a/homeassistant/const.py
+++ b/homeassistant/const.py
@@ -397,6 +397,7 @@
 PRESSURE_MBAR: str = "mbar"
 PRESSURE_INHG: str = "inHg"
 PRESSURE_PSI: str = "psi"
+PRESSURE_MMHG: str = "mmHg"
 
 # Volume units
 VOLUME_LITERS: str = "L"
diff --git a/homeassistant/util/pressure.py b/homeassistant/util/pressure.py
index 046b65122a972..41f5cc0b07aa7 100644
--- a/homeassistant/util/pressure.py
+++ b/homeassistant/util/pressure.py
@@ -11,11 +11,12 @@
     PRESSURE_PA,
     PRESSURE_PSI,
     UNIT_NOT_RECOGNIZED_TEMPLATE,
+    PRESSURE_MMHG,
 )
 
 _LOGGER = logging.getLogger(__name__)
 
-VALID_UNITS = [PRESSURE_PA, PRESSURE_HPA, PRESSURE_MBAR, PRESSURE_INHG, PRESSURE_PSI]
+VALID_UNITS = [PRESSURE_PA, PRESSURE_HPA, PRESSURE_MBAR, PRESSURE_INHG, PRESSURE_PSI, PRESSURE_MMHG]
 
 UNIT_CONVERSION = {
     PRESSURE_PA: 1,
@@ -23,6 +24,7 @@
     PRESSURE_MBAR: 1 / 100,
     PRESSURE_INHG: 1 / 3386.389,
     PRESSURE_PSI: 1 / 6894.757,
+    PRESSURE_MMHG: 1 / 133.3224,
 }
 
 
diff --git a/tests/util/test_pressure.py b/tests/util/test_pressure.py
index d92cc32542ff4..36c1f335af438 100644
--- a/tests/util/test_pressure.py
+++ b/tests/util/test_pressure.py
@@ -7,6 +7,7 @@
     PRESSURE_MBAR,
     PRESSURE_PA,
     PRESSURE_PSI,
+    PRESSURE_MMHG,
 )
 import homeassistant.util.pressure as pressure_util
 
@@ -20,6 +21,7 @@ def test_convert_same_unit():
     assert pressure_util.convert(3, PRESSURE_HPA, PRESSURE_HPA) == 3
     assert pressure_util.convert(4, PRESSURE_MBAR, PRESSURE_MBAR) == 4
     assert pressure_util.convert(5, PRESSURE_INHG, PRESSURE_INHG) == 5
+    assert pressure_util.convert(6, PRESSURE_MMHG, PRESSURE_MMHG) == 6
 
 
 def test_convert_invalid_unit():
@@ -69,3 +71,23 @@ def test_convert_from_inhg():
     assert pressure_util.convert(inhg, PRESSURE_INHG, PRESSURE_MBAR) == pytest.approx(
         1015.9167
     )
+
+
+def test_convert_from_mmhg():
+    """Test conversion from mmHg to other units."""
+    mmhg = 745
+    assert pressure_util.convert(mmhg, PRESSURE_MMHG, PRESSURE_PSI) == pytest.approx(
+        14.40585734588
+    )
+    assert pressure_util.convert(mmhg, PRESSURE_MMHG, PRESSURE_HPA) == pytest.approx(
+        993.25188
+    )
+    assert pressure_util.convert(mmhg, PRESSURE_MMHG, PRESSURE_PA) == pytest.approx(
+        99325.188
+    )
+    assert pressure_util.convert(mmhg, PRESSURE_MMHG, PRESSURE_MBAR) == pytest.approx(
+        993.25188
+    )
+    assert pressure_util.convert(mmhg, PRESSURE_MMHG, PRESSURE_INHG) == pytest.approx(
+        29.33069826777
+    )