It’s Jake Paul’s 28th trip around the sun, and we’re celebrating the YouTuber-turned-boxer's birthday by flexing his physique -- because why not showcase those gains?!

Paul has been livin' and lookin' like a champ since switching to boxing ... and despite the criticism, he’s boasting an impressive 11-1 record.

Of course, the biggest fight of his career so far happened only a few months ago ... when he faced Mike Tyson, one of the greatest boxers ever.

Paul won the bout by unanimous decision, insisting his victory was legit and not rigged.

The heavyweight boxer is excited to fight more opponents very soon but will enjoy his time away from it all to celebrate his special day, especially with his speed skater star girlfriend Jutta Leerdam, and possibly his brother Logan.

He'll also be hangin' with Donald Trump a few days after his bday ... as we confirmed The Problem Child will be at the Inauguration on Monday.

Happy birthday, Jakey!