The Kings announced Williams' new deal on Monday before facing
the Detroit Red Wings. The extension runs through 2014-15.
Williams, 29, was slated to be an unrestricted free agent July 1.
Williams, in his 10th NHL season, has 20 goals and 29 assists this season, with a plus-14 rating.
The Kings acquired him from Carolina in a three-way deal with Edmonton on March 4, 2009. He was part of the Hurricanes' 2006 Stanley Cup-winning team.
The Kings have secured a number of their core and up-and-coming players to longer-term deals. Defenseman Jack Johnson, 24, agreed to a seven-year contract extension on Jan. 9. Star center Anze Kopitar, 23, agreed to a seven-year contract extension in October 2008.
Los Angeles also acquired left wing Dustin Penner from Edmonton
Pierre LeBrun covers the NHL for ESPN.com. Information from The Associated Press was used in this report.