Ancaster—Dundas—Flamborough—Westdale was a provincial electoral district in southwestern Ontario, Canada.

It was created for the 2007 provincial election.

82.9% of the riding came from Ancaster—Dundas—Flamborough—Aldershot while 17.1% came from Hamilton West.

The riding included all of Hamilton west of a line running along Glancaster Road then to Garner Road then to a Hydroelectric Transmission Line then to Highway 403 to Hamilton Harbour.

In 2018, the district was dissolved into Hamilton West—Ancaster—Dundas and Flamborough—Glanbrook.