Oliver Mowat Biggar, CMG, KC (October 11, 1876 – September 4, 1948) was a Canadian lawyer and civil servant.

He was the second judge advocate general for the Canadian Militia and the first chief electoral officer of Canada.

[4] At the conclusion of World War I, Sir Robert Borden, then Canada's Prime Minister, invited Biggar to attend the peace conferences in Paris and Versailles as chief legal adviser and member of the Canadian delegation.

[15] As a former advisor to Prime Minister Borden and a delegate to the 1919 Paris peace conference where the League was founded, Biggar often consulted government officials and politicians on matters of international law.

[16] In 1924, Biggar was asked by Prime Minister William Lyon Mackenzie King to advise the Department of External Affairs on Canada's role in the League of Nations.

[19] The same year, he published a treatise comparing Canadian, British, and American patent law.

[20] During his time in private practice, Biggar appeared on behalf of a large variety of companies in numerous intellectual property cases.

[22] The outbreak of World War II and Canada's participation led Biggar to return to civil service.

In 1940, then Canadian Prime Minister Mackenzie King selected Biggar to be one of his senior advisors and appointed him to the newly created Canada-U.S.

This Board was co-chaired by Biggar as representative of Canada and Fiorello La Guardia, the former mayor of New York as the U.S.

[4][9][23] In 1942, Biggar was appointed Director of Censorship working under Minister of War Services Joseph Thorarinn Thorson.

He was tasked with creating a single agency for the purpose of effective wartime censorship out of what was then five separate operations.