Major James Mackerras MacDonnell (December 15, 1884 - July 27, 1973) was a Canadian soldier, lawyer and politician.

He was born in Kingston, Ontario, son of George W. Macdonnell and Mary Louise Philips. He was a Master at St. Andrew's College from 1904 to 1914 before becoming a trust company officer. He enlisted with the Canadian Expeditionary Force on September 24, 1914 at Valcatier, Qeubec .

He was elected in 1954 to the riding of Muskoka, Ontario representing the Progressive Conservative. He was defeated in the 1949 election. He was elected again in 1949 for the riding of Greenwood, Ontario until being defeated in 1962. From 1957 until 1959 he was Minister without Portfolio in John Diefenbaker's government.

In 1967 he was made a Companion of the Order of Canada.