"We are sleepless and delirious but so excited to share that, our miracle baby, arrived last night (11/7) via surrogate," the NBA star announced.
"Welcome to the party sweet girl!"
The couple had been trying to have a kid for years but Union has struggled with infertility, a battle she's talked about publicly.
In fact, 46-year-old Union has said she suffered 8 or 9 miscarriages.
She even addressed the topic in her book, 'We're Going to Need More Wine' -- saying, "For 3 years, my body has been a prisoner of trying to get pregnant."
But the good news ... they found a surrogate who carried the child for them -- and now they've got the baby they've been dreaming about!
Dwyane has 3 kids from other relationships but this is his first child with Gabrielle.