William Henry Withrow was born on August 6, 1839, in Toronto, Ontario.

He was a Methodist minister, journalist, and author. He was educated at Toronto Academy, Victoria College, Cobourg, and University of Toronto (B.A., 1863; M.A. 1864). Ordained in Hamilton in 1864, he served the churches in Waterford, Montreal, Hamilton, Toronto, and Niagara. He was originally connected with the Methodist New Connexion church but joined the Wesleyan Methodist Conference in 1867. In 1874, he became editor of the Canadian Methodist Magazine and Sunday School periodicals (Sunday School Banner, Sunday-School Advocate, and Onward), retaining that role until 1906. He was also their major article contributor. He received an honorary D.D. degree from Victoria College in 1882. Withrow was elected a Fellow of the Royal Society of Canada in 1883. He was a member of the Montreal Historical Society, the Senate and Board of Regents of Victoria University, the Senate of Wesleyan Theological College, Montreal, and the Senate of the University of Toronto. He wrote, "The Catacombs of Rome and Their Testimony Relative to Primitive Christianity" (1874).

In 1863, he married Sarah Ann Smith (1840–). He died on November 12, 1908, in Toronto, Ontario.