Mumballup is a locality in the South West region of Western Australia, situated between Collie and Boyup Brook, 221 kilometres (137 mi) south of Perth. The town is in the Shire of Donnybrook-Balingup.

It was the location of the death of the former premier of Western Australia James Mitchell in 1951, on a train on the Donnybrook–Katanning railway line. Mumballup was once a siding on the Donnybrook–Katanning railway but the railway line ceased operation in 1982.

It is a location on the Bibbulmun Track.