Sylvanus Stall (18 October 1847 – 6 November 1915) was a United States Lutheran pastor, most famous for his 1897 sex education and anti-masturbation book What A Young Boy Ought To Know and its many sequels.Stall was born in Elizaville, New York (now part of Gallatin). In 1866 he entered Hartwick Seminary, then Pennsylvania State University and the Union Theological Seminary in New York City. He was ordained a minister in 1874.Stall held a Doctor of Divinity degree.