Two days after welcoming him into the world, the parents of daughter North, 2, made the announcement on the fan site kimkardashianwest.com.
In a post titled “To Our Fans” the reality star wrote simply: “Saint West, 12.05.15, 8 pounds 1 ounce”.
It was accompanied by four emojis, depicting their family.
Within minutes of the eagerly-awaited announcement, memes poking fun at the name began circulating on Twitter and Instagram.
One of the most popular was a painting of Mary and Joseph kneeling over baby Jesus’s manger, with photos of Kim and Kanye’s faces pasted over the faces of Mary and Joseph.
Another meme placed the baby emoji – the same one used by Kim in her name announcement post – onto a painting of a saint, while one showed Kanye as Jesus, cradling the baby emoji.
One even jokingly suggested that Kim was smoking marijuana while picking out the names of her two children.
Kim, 35, revealed last week on her website that she was having trouble settling on a suitable name for her little boy.
One report said they were also seriously considering Legend, but Kim had categorically discounted opting for South.
“That would be the stupidest thing ever,” she said in one report.
“I don’t like South West, though, because North will always be better and she has a better direction.
“So I wouldn’t do that. I don’t think we’ll go with another direction.”
While her fans now await the first pics of Saint West, website TMZ is saying that Kim’s birth in the $US4000-a-night maternity suite at Cedars-Sinai Medical Centre in Los Angeles was a long and painful one.
The star allegedly had placenta accreta, a serious pregnancy condition in which the placenta grows too deeply into the uterine wall. This can cause severe blood loss after delivery.
A C-section is often advised with the condition, but Kim still managed to have a natural birth, the website added.
During an interview with C Magazine in August, the Keeping Up With The Kardashians star revealed that she may have to undergo a hysterectomy after the birth of her second child.
“They think I’ll have placenta accreta again, so if the placenta grows a little bit deeper than it did last time, then they are prepared to have my uterus removed, which is a little scary for me,” she shared.