Lupeni is a mining city in the Jiu Valley in Hunedoara County, Romania with a population of 31,409. It is one of the oldest and largest cities in the Jiu Valley. It is located on the banks of the West Jiu river within the Petroşani Depression, at a height varying between 630 m (in the east) and 760 m. The distance from Lupeni to Petrosani is 18 km (DN66A), and to Deva (the capital of Hunedoara County) is 114 km.
The name is derived from the Romanian "lup" meaning "wolf".
It was the site of the Lupeni Strike of 1929. The mining industry once employed 80% of the workers in the city, but after government subsidies were halted, it proved inefficient and much of it was closed down in 1997. The city's remaining active mine is the Lupeni Coal Mine managed by the Petroşani-based National Hard Coal Company.