The France Under-21 international arrives on a free transfer at the end of his contract with the Ligue 2 side, becoming the Gunners' first recruit of the summer on a "long-term" deal.
"Sanogo is a good young signing for us," manager Arsene Wenger told the club's official website. "He has shown that he has potential with his recent performances for Auxerre and also for the France Under-20s side. We are looking forward to Yaya joining us and continuing his promising development."
The youngster will link up with the Arsenal squad for training at the end of his involvement in the FIFA Under-20 World Cup in Turkey, having scored two goals as France progressed from the group stage.
Sanogo scored 11 goals in 24 games for Auxerre after coming up through the academy ranks.