Luncoiu de Jos (Hungarian: Alsólunkoj, German: Langenthal) is a commune in Hunedoara County, Transylvania, Romania.

It is composed of five villages: Dudești (Dudesd), Luncoiu de Jos, Luncoiu de Sus (Felsőlunkoj), Podele, and Stejărel (Szkrófa).

The commune at situated in the southwestern extremity of the Transylvanian Plateau, in the foothills of the Metaliferi Mountains, on the banks of the river Luncoiu.

The commune is traversed by the now-defunct Căile Ferate Române Line 209, which connected Brad to Deva.

The project was restarted in 1960, with a 301 m (988 ft) rail bridge over the river Mureș, and was completed in the mid-1980s.