The 35-year-old posted the much-anticipated name on Twitter along with emojis representing herself, Kanye West, North West and her son.
She simply wrote in capitals: "SAINT WEST".
SAINT WEST pic.twitter.com/xZGpY7z8KW— Kim Kardashian West (@KimKardashian) December 7, 2015
Within 15 minutes of posting her son's name, Kardashian West had received more than 26,000 retweets.
Some fans loved the "original" name, while others weren't so sure. The reaction was very mixed.
@KimKardashian why couldn't you name him something normal like jimmy or something— jess (@jessicahayIee) December 7, 2015
@Brandiiii24 lol well i guess its better than East— nick wood (@kushgodTGOD) December 7, 2015
@KimKardashian you lost your mind
but ily— em (@maradgon) December 7, 2015
And then came some compliments to the name...
@KimKardashian Congratulations ❤ Welcome Saint !!!!— Kati Ж Khlolover (@TrulyAKhloeKFan) December 7, 2015
@KimKardashian That's such an adorable name, congrats❤️— ☽ (@AGM00nlight) December 7, 2015
@KimKardashian beautiful name! Congrats Kimmy!— NOEL (@KingOfHotTopics) December 7, 2015
She wrote: "Saint West. 12.05.2015. 8 pounds 1 ounce."
Fans have been trying to guess the name of her newborn son since she announced the birth on Saturday.
With the majority of guesses involving directions ("Easton" and "South"), no one seemed to get it right.
Kardashian West announced the birth of her son on Twitter on 5 December by writing: "He's here".