Welby is a small town in the Southern Highlands of New South Wales, Australia, in Wingecarribee Shire. It was originally called Fitzroy. The town is located 1 km west of Mittagong and houses the local Southern Highlands RTA office. At the 2016 census, Welby had a population of 758.
A number of properties, built in both triple brick and stone with bull nose verandas, date back to 1850 and The old Fitzroy Progress Association Hall which was built in 1931 is still standing. It is now an antique shop - The Merchant of Welby.