Donald Cameron MacDonald (born 1913) is a long time Canadian politician.

MacDonald was a Conservative in his youth but became a democratic socialist after witnessing the social problems of the Great Depression. He worked for several years as a journalist and was employed by the Montreal Gazette from the mid-1930s until joining the Royal Canadian Navy in 1942. During World War II, Macdonald became editor of '"Canadian Digest, a magazine published by the military that provided a cross section of articles from Canadian periodicals and newspapers. He was also host of '"Serviceman's Forum, a regular series of broadcasts on the Canadian Broadcasting Corporation which were also aired by the British Broadcasting Corporation in which members of the military and civilian experts discussed issues of concern.

While on leave in Ottawa in 1942, MacDonald joined the Co-operative Commonwealth Federation. In 1946, he joined the national staff of the CCF and travelled the country as a party organizer. He was a candidate in the August 1953 Canadian election in the British Columbia riding of Kootenay East where he came in a strong third with 28% of the vote.

Later that year, he was persuaded to run for the leadership of the Ontario CCF and defeated Fred Young and Andrew Brewin for the position. MacDonald was elected leader of the Ontario Co-operative Commonwealth Federation in November 1953 and led it for 17 years and sat in the Ontario legislature as an MPP for 27 years. MacDonald took over the party in the middle of the Cold War and at the height of McCarthyism when socialism was viewed with suspicion. While the CCF had almost won power in Ontario ten years earlier winning 34 seats in the 1943 provincial election, by the time MacDonald became leader the party held only two seats. During his tenure MacDonald slowly rebuilt the party (which changed its name to the New Democratic Party in 1961) and provided it with an avuncular public face. MacDonald won a seat in the legislature in 1955 representing the Toronto riding of York South and fought for issues such as prison reform and universal public healthcare. Generally however, MacDonald emphasised pragmatism over socialism and tried to appeal to voters as a moderate reformer.

As the province's population became more urban and as social issues came to the forefront the NDP had a major breakthrough in the 1967 provincial election rising from seven seats to 20. This new success resulted in increasing pressure for new leadership as the party was seen as a potential victor and many activists felt a younger leader was needed to catch the mood of the times. Jim Renwick challenged MacDonald for the party leadership in 1968 but lost. In 1970, Stephen Lewis was able to martial support among the Steelworkers union with which his family had strong links (David Lewis had represented Steel as a labour lawyer for many years) and MacDonald decided not in June not to seek re-election as leader so as not to subject the party to a divisive fight. At the leadership convention that fall Stephen Lewis defeated Walter Pitman and succeeded MacDonald as Ontario NDP leader.

MacDonald remained in the legislature until 1982 when he resigned as an MPP in order to give newly elected leader Bob Rae an opportunity to enter the legislature. In 1986, MacDonald was appointed Chair of the Election Finances Commission, a post he retained until 1994.