The Grammy Award-winning singer announced he and his model wife had welcomed their fourth child on Friday morning ... and John delivered the happy news during a private performance that night, according to People.

"What a blessed day," John gushed to the audience. He then said he "didn't get a lot of sleep," but he "feels energized" despite long hours at the hospital.

The crowd went wild ... and some fans promptly took to social media to break the big news to the world.

One person wrote, "@johnlegend just told us he had a baby this morning."

The couple has 2 other children, Miles Theodore, 4, and Luna Simone, 6. You may recall, though, Chrissy sadly lost newborn Jack in September 2020.