88 Irish competitors are attending the games.

President Barack Obama earlier greeted the athletes by video from Kenya where is on an Africa tour.

A flaming torch carried from Greece was used to light the Coliseum’s Olympic beacon.

The games are for those with intellectual disabilities. Celebrities ranging from Colin Farrell to Stevie Wonder praised the athletes’ courage and determination.

It is the largest gathering of athletes in Los Angeles since the 1984 Summer Olympics.

The athletes will participate in 25 sports over nine days, ranging from weightlifting to the triathlon.

Mrs Obama told the athletes: ``My husband and I, we are so proud of you, so incredibly proud of you, and we love you all from the bottom of our hearts.''

She said the athletes were an example to the millions of people watching the event on television.

She was introduced by Special Olympian Tim Harris, who owns a restaurant in New Mexico that he said serves “breakfast, lunch and hugs!”

Mrs. Obama “knows the power of a hug,” he said, and shared one with the first lady.

About 6,500 athletes from 165 countries streamed into the Coliseum to cheers and roars. LA also hosted the Special Olympics in 1972.

Applause greeted the athletes, from some 400 in the US contingent to a handful each from smaller countries.

The groups wore distinctive colours but carried no national flags. However, Special Olympics athletes and Olympic gold medalists including swimmer Michael Phelps, diver Greg Louganis and skater Michelle Kwan together carried the Special Olympics flag.

The three-hour ceremony included Special Olympians at every level. Global ambassadors partnered with celebrities onstage and TV commentators.

Singer Stevie Wonder told the athletes: “You are the special people of the world. You are the ones that will make a difference every single day. Your courage, your desire to make the world better by showing your love ... (and) in the way that you carry yourself.”

At the beginning of the show, late-night television talk show host Jimmy Kimmel thanked the competitors and the international crowd of spectators for coming and joked about California’s long drought, saying he hoped they brought water.

“That Olympic flame they’re going to light will truly burn forever because we don’t have the water to put it out,” Kimmel said.

Kimmel also praised the athletes. “You remind me of how deeply lazy a man I am,” he said.

The games were the brainchild of President John Kennedy’s sister Eunice Kennedy Shriver, who held informal backyard competitions at her home before deciding to take the competition international in 1968. She said she believed everybody should have a chance to feel special.

Her daughter, Maria Shriver, also addressed the throng.

“She was so proud of you and wanted more than anything for you to be respected, valued, appreciated for who you are,” Shriver said. “Brave, good, kind, solid, and yes, smart human beings.”