Irwin Foster Hilliard (February 2, 1863 – November/December 1948) was an Ontario lawyer and political figure.
He represented Dundas in the Legislative Assembly of Ontario from 1914 to 1919 as a Conservative member.
He was born in Osnabruck Township, Canada West, the son of Thomas Foster Hilliard, and was educated in Morrisburg.
He articled in law in the office of James Pliny Whitney and was called to the bar in 1885.
He was Master in Chambers at Osgoode Hall until he returned to practice in Morrisburg in 1935.