"Psalm West," the reality star/mogul tweeted Friday.
She tweeted an image of what appears to be a series of Mother's Day texts and a photo of Psalm from her husband.
"Beautiful Mother's Day. With the arrival of our fourth child. We are blessed beyond measure," the texts read. "We have everything we need."
Psalm joins sisters North, 5, and Chicago 1, and brother Saint, 3.
There had been plenty of interest about the baby boy's name but the couple have a history of waiting a few days before revealing their children's names.