The annual list, released late Wednesday, places Winfrey third. The talk-show queen is worth $2.7 billion and earned $315 million in the past year, but beyond wealth Forbes takes into account executive position, creative influence and entrepreneurship.

No. 1 on the list is First Lady Michelle Obama. Forbes didn't calculate her and her husband's personal wealth or money earned in the last year, choosing instead to list in that category the country's national budget, which is $3.5 trillion.

After Winfrey, Lady Gaga, at No. 7, is the next media person on the list. She earned $62 million in the past year and, according to Forbes, "single-handedly reinvigorated pop music and pop culture." Next in media, at No. 9, is Knowles, who earned $87 million and whose music is a favorite of Michelle Obama's, according to Forbes.

Former "American Idol" judge DeGeneres is 10th on the list and earned $55 million. Forbes noted that she recently gave a $30,000 college scholarship to a gay teenager who challenged a high school policy against same-sex prom dates.

House Speaker Nancy Pelosi, who would be in line for the presidency after Vice President Joe Biden, is 11th on the list. Like Michelle Obama, her "money" category consists of the national budget.

Sarah Palin, who Forbes puts in the media category, is No. 16. Her title is "political maverick and commentator," but unlike most others on the list, her entry doesn't include a "money" category. Instead, she gets a "media buzz" category, which says she has 2.3 million Facebook friends and that if you search for her name online you'll get 44 million results.

Other media personalities on the list include Angelina Jolie (No. 21), Katie Couric (No. 22), Arianna Huffington (No. 28), Madonna (No. 29) and Sarah Jessica Parker (No. 45).

Obama's new ranking ends German Chancellor Angela Merkel's four-year reign at the top of the magazine's listing of the most influential women in the world.

Her quick track up the list was mirrored by that of her husband's former rival and now secretary of state Hillary Clinton, who moved up from 36th place last year to crack the top 10, taking fifth place.

Merkel, who is struggling with a rocky second term in office, was relegated to fourth place behind Kraft Foods CEO Irene Rosenfeld and talkshow host and media mogul Oprah Winfrey.

In compiling this year's list, the magazine said it opted to "look up and out into the broader culture." "Our assessment is based less on traditional titles and roles and more on creative influence and entrepreneurship."

At number six was Indra Nooyi, PepsiCo's chief executive and a perennial inclusion on the list, who fell three places from last year's rankings.

Rounding out the top ten was Gail Kelly, chief executive of WestPac, who came in at number eight this year.

Despite holding no official position, Forbes said Michelle Obama had proved "a true change-maker since taking lodge in the White House in 2008," citing her "Let's Move!" campaign aimed at reducing childhood obesity.

"The first African-American in the post, she's changed the face of the office (literally), and with consistently high approval ratings, she's given a new generation of girls and women around the world a role model," the magazine said.

Female US Supreme Court Justices Sonia Sotomayor (19), Elena Kagan (25) and Ruth Bader Ginsberg (31) made appearances, as did British Queen Elizabeth II (41), athlete Serena Williams (55) and Costa Rican President Laura Chinchilla (83).