Semlac is a commune located in the western part of Romania within Arad County. Situated near the border with Hungary, it lies in the south-western portion of the Arad Plateau along the large valley of the Mureș River.
The territory of the commune covers 8,311 hectares and consists of a single village, also named Semlac. The village is positioned approximately 37 kilometers (23 miles) from the city of Arad.