NEW YORK - Surprise, surprise. Grass is green, the world is round and Oprah Winfrey is the richest woman in entertainment.

The talk-show titan, who's amassed $1.5 billion over the course of her impressive career, has bested "Harry Potter" author J.K. Rowling and lifestyle guru Martha Stewart to take the No. 1 spot on Forbes.com's list of "The 20 Richest Women in Entertainment."

Rowling, who is finishing the seventh and final installment in her boy wizard series, ranks second with $1 billion. Stewart is third with $638 million.

Madonna ranks fourth with $325 million, followed by Celine Dion ($250 million), Mariah Carey ($225 million), Janet Jackson ($150 million), Julia Roberts ($140 million), and Jennifer Aniston and Jennifer Lopez (both $110 million).

Mary-Kate and Ashley Olsen, the twin actresses who started out on the '80s comedy "Full House" and created a multimedia empire, Dualstar Entertainment Group, are No. 11 with an estimated "combined net worth at around $100 million," Forbes said.

They're followed by Britney Spears, Judge Judy Sheindlin of TV's "Judge Judy," Sandra Bullock, Cameron Diaz, Gisele Bundchen, Ellen DeGeneres, Nicole Kidman, Christina Aguilera and Renee Zellweger.

Forbes said these rich ladies needed a minimum net worth of $45 million amassed over the course of their careers to make the list. It was posted Thursday on the Web site.