diff --git a/esphome/const.py b/esphome/const.py
index 6157ce32f7..b9c37a53a8 100644
--- a/esphome/const.py
+++ b/esphome/const.py
@@ -1042,6 +1042,7 @@ UNIT_KILOVOLT_AMPS_REACTIVE = "kVAR"
 UNIT_KILOVOLT_AMPS_REACTIVE_HOURS = "kVARh"
 UNIT_KILOWATT = "kW"
 UNIT_KILOWATT_HOURS = "kWh"
+UNIT_LITRE = "L"
 UNIT_LUX = "lx"
 UNIT_METER = "m"
 UNIT_METER_PER_SECOND_SQUARED = "m/s²"