the title from Leila Lopes of Angola during the two-hour competition at the Planet Hollywood casino on the Las Vegas Strip.
Culpo wore a tight navy blue mini-dress with a sequined bodice as she walked on stage for the competition's opening number. Later in the night, she strutted in a purple and blue bikini, and donned a wintery red velvet gown with a plunging neckline.
Culpo's coronation ends a long losing spell for the US in the competition co-owned by Donald Trump and NBC. An American had not won the right to be called Miss Universe since Brook Lee won the title in 1997.
Culpo was good enough during preliminary competitions to be chosen as one of 16 semifinalists who moved on to compete in the pageant's finale. Her bid lasted through swimsuit, evening wear, and interview competitions that saw cuts after each round.
She won over the judges, even after tripping slightly during the evening gown competition. Telecasters pointed it out but also noted her poised recovery.
Miss USA, Olivia Culpo, waves to the crowd after being crowned as Miss Universe during the Miss Universe competition in Las Vegas. AP Photo
Minutes before the middle child of five was crowned, she was asked whether she had she had ever done something she regretted.
"I'd like to start off by saying that every experience no matter what it is, good or bad, you'll learn from it. That's just life," she said. "But something I've done I've regretted is probably picking on my siblings growing up, because you appreciate them so much more as you grow older."
Miss Philippines, Janine Tugonon, came in second, while Miss Venezuela, Irene Sofia Esser Quintero, placed third.
All the contestants spent the past two weeks in Sin City, where they posed in hardhats at a hotel groundbreaking, took a painting lesson, and pranked hotel guests by hiding in their rooms.
Culpo was the first Miss USA winner from Rhode Island when she took the national crown in Las Vegas in June.
She grew up in Cranston with two professional musicians for parents and has played the cello alongside world-renowned classical musician Yo-Yo Ma. On her Miss Universe page, she said she hopes to pursue a career in film or television, and cites Audrey Hepburn as a role model because of her "generosity, intelligence and grace."
With Culpo's promotion, Miss Maryland Nana Meriwether becomes the new Miss USA.
The Miss Universe pageant was back in Las Vegas this year after being held in Sao Paulo in 2011. It aired live on NBC and was streamed to more than 100 countries.
Organizers had considered holding the 61st annual Miss Universe in the popular Dominican Republic tourist city of Punta Cana, but Miss Universe Organization President Paula Shugart said that country's financial crisis proved to be too much of an obstacle.
The panel of 10 judges included singer Cee Lo Green, Iron Chef star Masaharu Morimoto and Pablo Sandoval of the San Francisco Giants.
Asked on the red carpet whether he found playing in the World Series or judging the beauty pageant to be more difficult, Sandoval said both were hard.
Sharply dressed women and men, including a large contingent from South America, held banners and cheered on their favorite contestants.
The pageant started as a local revue in Long Beach, California, organized by Catalina Swimwear. It is not affiliated with the Miss America pageant and unlike that contest, does not include a talent section.
Contestants in the pageant cannot have been married or have children. They must be younger than 27 and older than 18 by Feb 1 of the competition year.
As Miss Universe, Culpo will receive an undisclosed salary, a wardrobe fit for a queen, a limitless supply of beauty products, and a luxury apartment in New York City.