James Aubrey Martensz, CBE, JP, UM (25 Sep 1885 - 19??) was a Ceylonese lawyer and politician.
He was a Proctor and Notary by profession and was a Justice of the Peace and Unofficial magistrate. In November 1947, he was nominated as a Member of the Ceylon House of Representatives, officiating as Deputy Chairman of the Committees, and on one occasion as Speaker of the House. He held the seat until January 1949, when he was appointed as Ceylon's first High Commissioner in Australia. 
In 1952, he was appointed Commander of the Order of the British Empire.