Taylor Swift celebrated big at her sold-out show at London's O2 Arena last night -- the 'Love Story' superstar revealed that she has surpassed 20 million album sales.

This mark in Swift's career is a notable one. The 20 million mark only represents full albums sold, including her self-titled record, 'Fearless,' 'Speak Now,' 'The Taylor Swift Holiday Collection' and 'Beautiful Eyes.' In reality, the singer has sold well over 30 million paid song downloads -- making her the No. 1 artist in digital sales in the history of the music industry.

Execs with Big Machine Records and Universal Music International presented 21-year-old Swift with a special plaque backstage at yesterday evening's show, honoring her big achievement, as pictured below.

Last night's London show wrapped up the overseas leg of her 2011 Speak Now World Tour, but the pop-country icon recently added 16 dates to the North American leg, which kicks off May 27 and wraps up with back-to-back Madison Square Garden performances this November.

The four-time Grammy winner is up for the fan-voted Entertainer of the Year award at this year's ACMs, which air this Sunday, April 3.