Welby is a small town in the Southern Highlands of New South Wales, Australia, in Wingecarribee Shire. The town is located 1 km west of Mittagong and houses the local Southern Highlands RTA office. At the 2011 census, Welby had a population of 736.
The town used to be known as Fitzroy. The old Fitzroy Progress Association Hall which was built in 1931 is still standing. It is now an antique shop - The Merchant of Welby.