The couple, who wed back in 2008, announced the happy news via Coleen’s Twitter page early this morning.
Wayne Rooney‘s wife, 31, revealed that she’d had a little boy while sharing the baby’s name with her 1.31 million followers.
Coleen and Wayne, 32, are already parents to Kai, eight, Klay, four, and two-year-old Kit.
The Liverpudlian tweeted: “So happy to welcome our baby boy… Cass Mac Rooney into the world weighing a healthy 8lb 10oz. He is beautiful.”
Wayne is yet to post anything on his social media pages while the birth date of the youngster remains unknown.
Many rushed to congratulate the pair online, with one user replying: “Congratulations – hope everyone is well.”
Two others continued: “Congratulations to you all. I’m waiting for the birth of my new grand baby due tomorrow,” and: “Congrats Coleen. He’ll be a great footy player like his dad or a model like his mum.”
Meanwhile, some seemed shocked that Coleen and Wayne had broken from tradition and not picked a name beginning with a K.
“You should have spelt it Kass to stick with the tradition,” one post read, as another stated: “No do Kass – keep with the K theme.”
Just hours earlier, Coleen had also posted about Valentine’s Day while sharing an adorable photo of her children and her spouse.
“Happy Valentine’s Day to my Boys… have a good one everybody,” she wrote alongside what appeared to be a holiday snapshot.
Coleen was thrown a surprise baby shower earlier this month in a gym in Liverpool, and was seen posing on exercise bikes.
She previously wrote on Instagram: “Surprise Baby shower yesterday… I absolutely loved it!
“Thanks so much girls and thank you @RiseCycling for perfect venue, @neilnoa.”
Coleen was seen in a sash while her bump was mostly hidden in black skinny jeans and a matching top.
The stars welcomed their first child back in November 2009 and they revealed they were pregnant for a fourth time back in August.