Cullerin is a small township in the Southern Tablelands of New South Wales, Australia. It is on the Old Hume Highway and Main South railway line in Upper Lachlan Shire. The Cullerin railway station opened in 1880 and closed in 1973. At the 2016 census, it had a population of 38.

Cullerin is at the summit of a 15 km (9.3 mi) stretch of ruling grade of the Main Southern Rail line. It lies a few kilometres west of the Great Dividing Range. The Lachlan River and other rivers to the west flow inland, while the Wollondilly River and other rivers to the east flow to the Pacific.