Robitaille, who had three stints covering 14 seasons with the Kings, was honoured a year and a day after he set the franchise record for goals with a hat trick against the Atlanta Thrashers at Staples Center. The eight-time all-star scored 557 goals with the Kings, seven more than Marcel Dionne did.
"It wasn't about scoring goals, it wasn't about money, it wasn't about fame. I just wanted to play hockey and play in the NHL," said Robitaille, who got his nickname "Lucky" from former Kings teammate Dave "Tiger" Williams.
"I wasn't the fastest player and I had flaws, but I was a student of the game and every day I was grateful to live my dream. I heard your chants every time I touched the puck or took a shot."
Rogie Vachon (30), Dionne (16), Dave Taylor (18) and Coyotes coach Wayne Gretzky (99) are the other Kings to have their numbers retired.
The rookie of the year in 1987, Robitaille retired at the end of last season, his 19th, as the NHL's leading career scorer among left wings.
He had 1,154 total points in 1,077 regular-season games with the Kings and is still a vital member of the organization, having been named as alternate governor for the club on Nov. 13.
The other 10 players who wore No. 20 with the Kings were Bob Pulford, Ray Ferraro, Mark Hardy, Brad Selwood, Gordon Labossiere, Ron Anderson, Scott Garland, Don Howse, Larry Playfair and Steve Larouche. They combined to score 174 goals for the franchise - 383 fewer than Robitaille did.
Robitaille, No. 10 on the NHL's career goals list, scored a career-high 63 the year the Kings went to the finals for the only time in their 40-year history. They lost in five games to the Montreal Canadiens, Robitaille's hometown team. But he eventually got his name chiselled into the Cup in 2002 with the Detroit Red Wings.
The Staples Center crew painted a large "20" on the ice behind each net, and all of the Kings' players skated out for the pre-game warmup wearing jerseys with Robitaille's name and numeral on the back and a commemorative patch on the front.
The one-hour ceremony included video tributes from Mark Messier and Lakers star Kobe Bryant, and Robitaille was presented with a truck, two snowmobiles and a painting of himself with the four other retired numbers in the background.
Among those walking the red carpet to centre ice were NHL commissioner Gary Bettman and 19 former Kings players including Vachon, Gretzky, Larry Robinson, Jimmy Carson, Butch Goring Bernie Nicholls, Jari Kurri, Marty McSorley and Bob Berry.
Barry Melrose, who coached the Kings to the Stanley Cup finals in 1993, also was on hand.
"When you went to see Luc play, you never felt cheated," Melrose told the sellout crowd. "Every time I watched Luc Robitaille play, he reminded me of why I love this game so much."
Taylor wasn't able to make it because of the death of his father. Neither was Dionne, Robitaille's mentor and boyhood idol, who had a family commitment but promised him he would be in Toronto for Robitaille's eventual Hall of Fame induction. Both sent written messages that were read by Kings longtime play-by-play man Bob Miller.