Southill, Weymouth is a modern suburb of Weymouth, Dorset, England, and lies about 2 miles (3 km) north of the town centre. It was developed on the western shore of Radipole Lake in several phases from the 1960s onwards.
At its centre lay a post office, confusingly and wrongly named South Hill Post Office, but this closed in January 2007. There is a small shopping centre, a community centre, a church and a pub, the John Gregory. A primary school was built to serve the new estate in the 1970s.
Southill is part of the parish of Radipole, the hill itself coming between Radipole and Weymouth.