John Hume Agnew (October 18, 1863 – November 9, 1908) was a politician in Manitoba, Canada. He served in the Legislative Assembly of Manitoba from 1903 until his death as a member of the Conservative Party, and was a prominent cabinet minister in the government of Rodmond Palen Roblin.
Agnew was born in Prince Albert, Canada West (now Ontario), and was educated at the Toronto Collegiate Institute and Upper Canada College. He worked as a barrister. Agnew was a school trustee in Virden, Manitoba for over ten years, and was a councillor for two. In religion, he was a member of the Church of England.
He was first elected to the Manitoba legislature in the 1903 provincial election, defeating Liberal candidate F.W. Clinigan by 25 votes in the Virden constituency. He was appointed to Roblin's cabinet on March 2, 1904 as Provincial Treasurer. New cabinet appointees were required to seek a renewed mandate from their electors in this period of Canadian history, and Agnew was returned for Virden without opposition on March 12.
He was re-elected with an increased majority in the 1907 election, and was retained as Provincial Treasurer in the legislative sitting that following. He died in office in 1908.