The 21-year-old arrives in Turin on a four-year deal from the Swiss outfit, who finished third in the Super League last season.
"Torino Football Club is pleased to announce that it has acquired outright from Young Boys the rights of the player Josef Alexander Martinez," a statement on the Italian club's official website read.
"The Venezuelan striker has signed a contract that will bind him to the club until June 30, 2018."
Martinez had a spell on loan at Thun last season, scoring eight goals in 18 appearances.
He then returned to his parent club and netted three in a further 18 games as Young Boys qualified for next season's UEFA Europa League.
Torino - who are also set to play in the Europa League after Parma were excluded due to licensing issues - have a void to fill in attack following the departure of Ciro Immobile to Borussia Dortmund.
