Giovanni was born to an impoverished rural family in Castelnuovo, Piedmont. Patronage from clerics allowed him to be ordained priest in 1841. He devoted himself to improve the life and education of the many homeless peasant teenage boys in and around Turin, hundred of whom were attracted to the city by the Industrial Revolution.

In 1864 he founded the Salesian Fathers religious order. At Bosco's death the Salesian "oratoires" numbered about 250. He was beatified in 1924, and declared a Saint of the Catholic church in 1934.

Bosco is one of the many homosexuals who found in the Catholic church a family and a "mission". Quite surely he was a paedophile who, possibly, succeeded in sublimating his attraction to young boys into a socially useful undertaking.