Major James William Coldwell, PC , CC (December 2, 1888–August 25, 1974), usually known as M.J., was a Canadian socialist politician, and leader of the Co-operative Commonwealth Federation party from 1942 to 1960. Major was his first name, not a military title.
Coldwell was born in England. He moved to Canada in 1910 and became a school administrator in Regina, Saskatchewan. He became known nationally as a leader of teacher's associations from 1924 until 1934. He was elected to the city council in Regina and developed links with labour and farmers organizations.
When the Saskatchewan Farmer-Labour Party was formed in 1932, Coldwell was chosen to be its first leader. The party fought the 1934 provincial election under Coldwell's leadership, and won five seats in the Legislative Assembly of Saskatchewan, making it the official opposition to the Liberal government. Coldwell was defeated in his election bid. After the election, the party affiliated itself with the Co-operative Commonwealth Federation, and became the Saskatchewan CCF.
In the 1935 federal election, Coldwell was elected to the House of Commons as Member of Parliament (MP) for the riding of Rosetown-Biggar. He split with CCF leader J.S. Woodsworth when World War II broke out in 1939. Woodsworth, a pacifist, opposed the war effort, while Coldwell and the rest of the CCF caucus supported the war. When Woodsworth resigned as CCF leader in 1942, shortly before his death, Coldwell was unanimously elected the party's new leader. He lead the party through five general elections.
In 1967, he was made a Companion of the Order of Canada. In 1964 he became a member of the Queen's Privy Council for Canada.