John Dunlop Millen (1877 – 1 August 1941) was an Irish-born Australian politician. Born in Derry, he migrated to Australia as a child and was educated at the University of Sydney, becoming an engineer and mine manager in Tasmania. In 1919, he was elected to the Australian Senate as a Nationalist Senator for Tasmania. In 1931, the Nationalist Party became the United Australia Party, which Millen duly joined. He held his Senate seat until 1937, when he was defeated. He became a company director, and died in 1941.[1]