Britney Spears is back at No. 1.

For the first time in more than five years, the ailing singer has topped the Billboard charts. Her newest album, Circus, has already sold more than half a million copies during the week ending Sunday, good enough for the #1 position.

This gives Brit the second biggest female debut of '08, topping Mariah Carey, Miley Cyrus, Madonna, Janet Jackson and Beyoncé and only trailing Taylor Swift.

Back in October, Britney set the stage for a comeback as "Womanizer" became her first chart-topping single since "... Baby One More Time" a decade ago.

"Womanizer" also set a record for the biggest digital sales debut by a female artist (286,000 copies) since Nielsen started tracking downloads in '03.

"A year ago, did anyone think that today she would be able to come out with an album that would not only just debut at No. 1, but sell half a million copies in its first week?" asks Billboard Senior Chart Manager Keith Caulfield.

It's not just album and song sales soaring, because according to Britney Spears' official website, "This tour is selling out like hot cakes!"

So expect the ludicrously expensive "circus" to come to town soon.