As of September 2021, the most followed person on Twitter is currently the former President of the United States, Barack Obama, with over 131 million followers. He is followed closely by the current President, Joe Biden, who has over 31 million followers. Other popular figures on Twitter include singers Katy Perry, Justin Bieber, and Rihanna, and footballer Cristiano Ronaldo, all who have over 100 million followers. It is important to note that the number of followers can fluctuate over time, and there may be some discrepancy in the exact numbers due to inactive accounts, bots, and other factors.