William X. Kienzle was born in Detroit, Michigan. He was ordained to the priesthood in 1954 and spend twenty years as a Roman Catholic parish priest. Kienzle left the priesthood in 1974, largely because of disagreeing with its refusal to remarry divorcees and to marry his wife, Javan. He became an editor of MPLS magazine in Minneapolis and later moved to Texas, where he was director of the Center for Contemplative Studies at the University of Dallas.

In 1974 he married Javan Herman Andrews, a journalist from the Detroit Free Press, until his sudden death after a heart attack on December 28, 2001.

Kienzle was the author of twenty-four crime fiction/mystery novels featuring "Father Robert Koesler", a Catholic priest who doubles as a detective. One of his best known novels is The Rosary Murders (1978), which was made into a movie starring Donald Sutherland as Father Robert Koesler, which was released in 1987. Most of Kienzle's books take place, at least partly, in Detroit, Michigan.