Semlac (Hungarian: Szemlak) is a commune located in Arad County, in the western part of Romania, near the border with Hungary, is situated in the south-western part of the Arad Plateau, in the large valley of the Mureș River.

It is composed of a single village, Semlac, situated 37 km (23 mi) from Arad.

According to the 2011 census, the commune has 3,667 inhabitants, out of which 78.4% were ethnic Romanians, 8.4% Roma, 2.67% Hungarians, and 2.32% Germans.

Until the Treaty of Trianon, Arad County belonged to the district of Pecica.

The economy of the commune is mainly agrarian, the locality is well known in the region as an important grain-bearing vegetable-growing place.