diff --git a/homeassistant/components/number/__init__.py b/homeassistant/components/number/__init__.py
index 5a48d00d4da..523cd50a6ed 100644
--- a/homeassistant/components/number/__init__.py
+++ b/homeassistant/components/number/__init__.py
@@ -296,7 +296,7 @@ class NumberDeviceClass(StrEnum):
     VOLTAGE = "voltage"
     """Voltage.
 
-    Unit of measurement: `V`
+    Unit of measurement: `V`, `mV`
     """
 
     VOLUME = "volume"
diff --git a/homeassistant/components/sensor/__init__.py b/homeassistant/components/sensor/__init__.py
index 12f49766834..e893c0f9e79 100644
--- a/homeassistant/components/sensor/__init__.py
+++ b/homeassistant/components/sensor/__init__.py
@@ -88,6 +88,7 @@ from homeassistant.util.unit_conversion import (
     BaseUnitConverter,
     DataRateConverter,
     DistanceConverter,
+    ElectricPotentialConverter,
     InformationConverter,
     MassConverter,
     PressureConverter,
@@ -390,7 +391,7 @@ class SensorDeviceClass(StrEnum):
     VOLTAGE = "voltage"
     """Voltage.
 
-    Unit of measurement: `V`
+    Unit of measurement: `V`, `mV`
     """
 
     VOLUME = "volume"
@@ -476,6 +477,7 @@ UNIT_CONVERTERS: dict[SensorDeviceClass | str | None, type[BaseUnitConverter]] =
     SensorDeviceClass.PRESSURE: PressureConverter,
     SensorDeviceClass.SPEED: SpeedConverter,
     SensorDeviceClass.TEMPERATURE: TemperatureConverter,
+    SensorDeviceClass.VOLTAGE: ElectricPotentialConverter,
     SensorDeviceClass.VOLUME: VolumeConverter,
     SensorDeviceClass.WATER: VolumeConverter,
     SensorDeviceClass.WEIGHT: MassConverter,
@@ -537,7 +539,7 @@ DEVICE_CLASS_UNITS: dict[SensorDeviceClass, set[type[StrEnum] | str | None]] = {
     SensorDeviceClass.VOLATILE_ORGANIC_COMPOUNDS: {
         CONCENTRATION_MICROGRAMS_PER_CUBIC_METER
     },
-    SensorDeviceClass.VOLTAGE: {UnitOfElectricPotential.VOLT},
+    SensorDeviceClass.VOLTAGE: set(UnitOfElectricPotential),
     SensorDeviceClass.VOLUME: set(UnitOfVolume),
     SensorDeviceClass.WATER: {
         UnitOfVolume.CENTUM_CUBIC_FEET,
diff --git a/homeassistant/util/unit_conversion.py b/homeassistant/util/unit_conversion.py
index 623b70da1a8..fc58014c143 100644
--- a/homeassistant/util/unit_conversion.py
+++ b/homeassistant/util/unit_conversion.py
@@ -4,6 +4,7 @@ from __future__ import annotations
 from homeassistant.const import (
     UNIT_NOT_RECOGNIZED_TEMPLATE,
     UnitOfDataRate,
+    UnitOfElectricPotential,
     UnitOfEnergy,
     UnitOfInformation,
     UnitOfLength,
@@ -137,6 +138,21 @@ class DistanceConverter(BaseUnitConverter):
     }
 
 
+class ElectricPotentialConverter(BaseUnitConverter):
+    """Utility to convert electric potential values."""
+
+    UNIT_CLASS = "voltage"
+    NORMALIZED_UNIT = UnitOfElectricPotential.VOLT
+    _UNIT_CONVERSION: dict[str, float] = {
+        UnitOfElectricPotential.VOLT: 1,
+        UnitOfElectricPotential.MILLIVOLT: 1e3,
+    }
+    VALID_UNITS = {
+        UnitOfElectricPotential.VOLT,
+        UnitOfElectricPotential.MILLIVOLT,
+    }
+
+
 class EnergyConverter(BaseUnitConverter):
     """Utility to convert energy values."""