Winfrey beat golfer Tiger Woods into second spot, with Madonna in third place following a successful tour.
British stars in the top 20 include Sir Elton John, the Rolling Stones and David Beckham.
The list, published annually, takes into account celebrities' earnings, internet presence and press, TV and radio coverage.
Winfrey, whose chat show is watched by 30 million viewers each week in the US, regained her top spot - which she lost last year to Tom Cruise - with estimated earnings of $260m (£131.8m).
"A combination of strong financials and her enduring influence on the US public, which could see her affecting the outcome of next year's US elections, is enough to propel her back into the top spot," said a Forbes spokeswoman.
Other British entries include JK Rowling in 48th place, with Harry Potter film stars Daniel Radcliffe and Emma Watson in 79th and 97th place respectively.
Heiress and reality TV star Paris Hilton, who was number 56 on last year's list, failed to make the top 100 for 2007.
Madonna fell out of last year's top 100 list but her Confessions tour last summer significantly boosted her earnings.
It was named the highest-earning show by a female artist by US magazine Billboard.