Keane has agreed a two-year contract with the MLS side and will become a team-mate of David Beckham.
“I am delighted, honoured and very excited to be joining the LA Galaxy,” Keane told his new club’s official website.
“I have always wanted to come and play in MLS so it’s the perfect combination for me and a dream come true.
“My family and I have already been made to feel very welcome in telephone calls from (president of Galaxy owners AEG) Tim Leiweke and (Galaxy general manager and head coach) Bruce Arena.
“Also when David Beckham came and trained at Spurs recently he couldn’t speak highly enough about the Galaxy, their fans and the league in general, so I can’t wait to get over and get started.”
Keane added: “I have already discussed football with Bruce Arena and I know exactly what he wants from me.
“I am fit, fresh and ready to go. I’ve come here to score goals and help this team achieve their goals.
“This is a massive opportunity for me in my career. I aim to grab it with both hands and hopefully help give the Galaxy fans what they want.”
