The Spain international, who has been touted as a potential new signing for the Gunners in recent weeks, has eventually put pen to paper for an undisclosed fee.
"The club has one of the best managers in football and their style of play is recognised and admired all over the world," Cazorla told the club's official website.
"I'm so excited to be joining one of the greatest teams in Europe and also in the Premier League. I will do my best to help Arsenal challenge for trophies and make all the supporters happy."
Arsenal boss Arsene Wenger added: "Cazorla is a great signing for us. He is a player with good experience at both club and international level, who will add significant quality to our squad.
"He is a versatile, attacking midfield player who can play comfortably on either side of the pitch or centrally. He has good pace, is technically gifted and will be a huge asset to Arsenal Football Club. We are delighted that he is joining us."
Cazorla is the North London club's third signing of the summer following the acquisitions of Lukas Podolski and Olivier Giroud.