Jessie James Decker and Eric Decker are now a party of six … they’ve officially welcomed their new bundle of joy into the world!

Jessie made the announcement on IG Sunday, writing … “Our beautiful boy is here 💙 Denver Calloway Decker,” … attaching a snap of her cradling her newborn with Eric looking over him in pure awe and wonder.

JJD gave us another snap of the sleeping younger … who tipped the scales at a healthy 8.7 pounds upon his arrival.

The happy couple — who are already mom & dad of daughter Vivianne and sons Eric Jr. and Forrest — kept their news under wraps for a solid 10 days before sharing it with the world … listing his official birth date as 9 February.

Heidi Montag, Kim Zolciak-Biermann and Jennifer Love Hewitt were just a few of the couple’s celeb pals who dropped congratulatory comments … along with the rest of their fans who gave a big thumbs up to the lil one’s name choice. Denver’s a massive hit!

Jessie’s pregnancy was announced in August … and caught everyone by surprise, including Eric, who’d been considering getting a vasectomy after their third — but he never went through with it.

Jessie spilled the tea in an IG Q&A shortly after the big reveal … sharing that Eric was so shocked he thought she was pulling a prank on him. In fact, he was convinced her then-pregnant sister had peed on the stick to fake her own results.

No jokes or gags here … this kid’s the real McCoy. Just don’t ask Eric about baby no. 5!