Lilhac (French pronunciation: [lijak]) is a commune in the Haute Garonne department in southwestern France.

Lilhac lies roughly 65 km southwest from Toulouse.

Its altitude at the highest point is 380 metres, and covers an area of 730ha or 7.3 km².

The river Touch has its source in the commune.

The local church, Eglise St-Quitterie, dedicated to Saint Quiteria, dates to before the 18th century.