As part of the trade, Carolina acquired forward Erik Cole and a fifth-round selection in the 2009 draft from Edmonton, and the Oilers received a second-round pick in the 2009 draft from the Hurricanes.
The trade came one day after the Kings' 5-4 loss at Columbus, a defeat that concluded a 1-3-0 road trip and left the Kings in 13th place in the West, seven points out of a playoff spot with 19 games remaining.
Williams, 27, has played in 32 games with the Hurricanes this season, posting 3 goals and 7 assists with 9 penalty minutes. The 6-foot-1, 195-pounder is currently on the injured reserve list due to a broken hand sustained on Feb. 15.
Williams, a member of Carolina's Stanley Cup winning team in 2006 and an All-Star in 2007 when he scored a career-high 33 goals, has played in 491 career NHL games with the Hurricanes and the Philadelphia Flyers, the team that selected him with the 28th pick in the 2000 draft. He has 124 goals and 192 assists with 325 penalty minutes. In 42 playoff games, Williams has 8 goals and 16 assists with 46 penalty minutes.
Williams' best seasons came in 2005-06 and 2006-07. In '05-06, he played in all 82 games and had a career-best 76 points (31-45-76). The next season, he also played in all 82 games and had 67 points, including a career-high 33 goals. He signed a five-year contract with the Hurricanes prior to the 2006-07 season.
O'Sullivan, 24, played in 62 games with the Kings this season and had 14 goals and 23 assists with 16 penalty minutes. The Kings acquired O'Sullivan from Minnesota in 2006, and he had 41 goals and 68 assists in 188 games with Los Angeles.
Earlier in the day, the Kings re-signed defenseman Sean O'Donnell to a one-year contract and goaltender Erik Ersberg to a two-year deal. The Kings also sent veteran defenseman Tom Preissing, who was placed on waivers this week but went unclaimed, to Manchester of the American Hockey League.
In another deal, the Oilers obtained forward Ales Kotalik from the Buffalo Sabres in exchange for the second round choice in the 2009 Entry Draft acquired earlier from the Carolina Hurricanes.
Kotalik has appeared in 56 games with Buffalo this season and was the Sabres' fifth leading scorer with 13 goals and 19 assists. Among his goals were 8 power-play goals and 1 game-winning goal. The 6-foot-1, 227-pound right winger leads the NHL with four shootout deciding goals this season and he is tied for the NHL record for most career shootout deciding goals with nine.
Now in his seventh NHL season since turning pro with Buffalo in 2001-02, the 30-year-old right winger has scored 114-126-240 with 267 penalty minutes in 426 career NHL games. He has scored 6-9-15 with 16 penalty minutes in 34 playoff games with Buffalo.