a river in Kaluga Oblast, RSFSR (sources in Moscow Oblast), a right tributary of the Protva (Oka Basin).
The Luzha is 159 km long and has a basin area of 1,400 sq km. It is fed primarily by snow. High water is in April and May; the range in the water level is 6.1 m. The river freezes over in November (less often, in December) and thaws in April. The city of Maloiaroslavets is located on the Luzha.