Sylvanus Stall (18 October 1847 – 6 November 1915)[2] 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.

He was initially a pastor in Cobleskill, New York (1874–77), Martins Creek, Pennsylvania (1877–80) and Lancaster, Pennsylvania (1880–87)[2] (including running a Sunday School attended by H. L. Mencken[3]), but quit in 1887 to edit a church newspaper, The Lutheran Observer, and start writing books.

[2] After several small-selling books, he released the enormously popular What A Young Boy Ought To Know, a book on sexual hygiene, warning young boys of the purported dangers of masturbation.

[5] A cylinder collection was also offered for sale; Loompanics described this as possibly being the first audiobook.

[7] With Dr. Mary Wood-Allen: Media related to Sylvanus Stall at Wikimedia Commons