King, who turned 33 last week, has played only three games for the second-placed Rabbitohs this season, having had to fight back from two broken arms in less than a year.
The wild-haired winger will depart after a glittering 10-year career since making his first grade debut for Melbourne.
King played in two grand finals for the Storm in 2006 and 2007. They won in 2007 but the title was subsequently stripped from the club over the salary cap scandal.
He also helped NSW to a State of Origin series win in 2005 before moving the UK Super League to star for Warrington as the club won back-back Challenge Cup finals in 2010 and 2011.
King was a late starter in the game having walked away from Cronulla when he was 21 after becoming disillusioned with a lack of opportunities, taking up work as a garbage collector and a barman.
"First of all I would like to thank (Storm coach) Craig Bellamy, (Warrington coach) Tony Smith and of course (South coach) Michael Maguire," King said.
"They have all helped me greatly in achieving my goals over the years.
"Then I would like to thank every teammate I've ever played with, right back to the under 7s at the Casino Cougars.
"I will look forward to the next chapter in my life once this season is over, and hopefully I can maintain a connection with the sport I love in Rugby league, and the club I've grown to love over the past two years in South Sydney."