The billionaire cosmetic guru beat the former most followed woman on IG, Ariana Grande who is now in the second position.
Grande is tied with music star Selena Gomez with 289 million followers each.
Jenner who has been on a lowkey on the social media platform only broke her social-media silence on Christmas Eve, sharing a photo of her mother, Kris Jenner.
Instagram was created by Kevin Systrom and Mike Krieger in 2010.
It was bought by Facebook in a $1B deal in 2012.
Other popular users of the platform include footballers Christiano Ronaldo with 390 million followers and Lionel Messi with 300 million followers.