Keane, the Republic of Ireland’s record goalscorer with 65 goals in a record 139 appearances for his country, is now in his fifth season in the MLS.
The 34-year-old has scored 55 times in 91 games for Galaxy and will remain in the USA for an extended period, although the club have not released details of the extended deal.
“We’re very pleased Robbie will continue to be a member of the Galaxy in the coming years,” Galaxy head coach and general manager Bruce Arena told the club’s official website.
“He has been one of the key pieces in our success over the past five seasons. We look forward to even more success with Robbie as a member of our team.”
Keane was named the MLS’ Most Valuable Player (MVP) last season and has won three MLS Cup Championships on three occasions.
He will join up once again with former Liverpool player Steven Gerrard in California, having spent a short period of time with him at Anfield before returning to former club Tottenham in 2009.