Charles James Mayer, PC (born April 21, 1936) is a Canadian businessman and former federal Minister of Agriculture.

He was educated at the University of Saskatchewan and became an agrologist and farmer. Politically active, Mayer was president of the Manitoba Beef Growers Association before entering the House of Commons of Canada as a Progressive Conservative Member of Parliament in 1979. He represented the Manitoba riding of Portage—Marquette (later Lisgar—Marquette) until his defeat in 1993.

He served in the Brian Mulroney government as Minister of State for the Canadian Wheat Board until 1987 and then was Minister of State for Grains and Seedoils until 1993 also serving as Minister of Western Economic Diversification from 1989. In early 1993 he was promoted to Minister of Agriculture and was retained in that position during the short-lived government of Mulroney's successor, Kim Campbell.

25th Ministry – Cabinet of Kim Campbell Cabinet post (1) Predecessor Office Successor cont'd from 24th Ministry Minister of Agriculture1993 Ralph Goodale 24th Ministry – Cabinet of Brian Mulroney Cabinet post (1) Predecessor Office Successor Bill McKnight Minister of Agriculture1993 cont'd into 25th Ministry