The US singer has 3m more followers than her nearest rival Justin Bieber, but how many are real?
The US singer-songwriter Katy Perry has become the first person to reach 100m followers on Twitter.
The website posted a video compilation of her tweets since she joined in 2009 along with a message saying "Today, we #WITNESS history".
Witness is the name of Perry's new album.
The Canadian singer Justin Bieber has the second highest number of followers at 96.7m with Barack Obama in third place with almost 91m.
The rest of the top 100 accounts are mostly made up of singers, sports stars, media companies and a few politicians, according to the website Twitter Counter.
US president Donald Trump is the most-followed current leader, in 33rd place with 32.4m followers. Two places behind him - after the boy band One Direction - is Indian Prime Minister Narendra Modi with 30.7m followers.