The 'Judas' singer reached the milestone earlier today and immediately took to the social networking website to thank fans for their continued support.
She wrote: "10MillionMonsters! I'm speechless, we did it! Its an illness how I love you. Leaving London smiling. (sic)"
The 25-year-old also posted a glamorously styled picture of herself bidding farewell to reporters in the capital.
GaGa became the first celebrity to win nine million Twitter followers in March after overtaking Britney Spears as the most popular star on the site last August.
The 'Edge Of Glory' artist will also celebrate the online achievement with a set at Radio 1's Big Weekend in Carlisle today.
The star yesterday used the social networking site to unveil the artwork for 'Hair', the latest promotional single to be released from her upcoming album Born This Way.
