Peter Gordon MacKay, PC, QC, MP (born September 27, 1965) is a lawyer and politician from Nova Scotia, Canada. He is the Member of Parliament for Central Nova and currently serves as Minister of National Defence in the Cabinet of Canada.

MacKay was the final leader of the Progressive Conservative Party of Canada (PC Party). On October 15, 2003, he and Canadian Alliance leader Stephen Harper agreed to merge the two parties, forming the Conservative Party of Canada. In December 2003, members of both parties ratified the merger.

MacKay was born in New Glasgow, Nova Scotia, the son of PC cabinet minister and lumber businessman Elmer MacKay. His mother, Macha MacKay, is a psychologist and peace activist, living in Wolfville, Nova Scotia, where he grew up with his three siblings. MacKay graduated from Horton District High School in Greenwich, Nova Scotia, and then went on to graduate with a Bachelor of Arts degree from Acadia University in 1987, MacKay then studied Law at Dalhousie University and was called to the Nova Scotia Bar in June 1991. He worked for Thyssen Henschel, steel producer, in Halifax, Nova Scotia, and in Düsseldorf and Kassel, Germany.