William D. Casey (born February 19, 1945) is a Canadian politician from Nova Scotia who served as a Member of Parliament (MP) in the House of Commons of Canada.

In 2007, Casey was expelled from the party for voting against the 2007 budget, but he was reelected as an Independent in the 2008 election and sat as such until he resigned his seat in 2009 to work on behalf of the Nova Scotian government for provincial interests in Ottawa.

In common with almost every other PC Member of Parliament (MP) in the 1993 election he lost his seat, in his case being defeated by Liberal candidate Dianne Brushett.

He was the deputy whip of the Official Opposition from 2004 until the 2006 election, and had served as the Conservative critic of Transport, International Trade, National Revenue, and Foreign Affairs in the past.

[5] In October 2007, the Conservative Party riding association in Cumberland—Colchester—Musquodoboit Valley renominated Casey as its candidate for the 2008 election.

The party's head office refused to accept Casey's nomination, and suspended the association's board.

[7] On September 4, the Green Party of Canada declared its support for his candidacy and announced that they would not field a candidate against him in the 2008 election.