William Barton Northrup, KC (October 19, 1856 – October 22, 1925) was a Canadian lawyer and politician. Born in Belleville, Canada West, the son of Anson Gilbert Northrup and Jane C. Balster, Northrup was educated at the Upper Canada College and the University of Toronto, where he received a Bachelor of Arts degree in 1877 and a Master of Arts degree in 1878. A lawyer he was head of the firm of Northrup & Roberts, in Belleville. He was created a King's Counsel in 1903. From 1918 to 1924, he was the Clerk of the House of Commons.