Ciara Serenades Russell Wilson For QB's 33rd Birthday, 'I Love You!'

Ciara didn't let a road trip to Washington prevent her from celebrating her man's birthday ... 'cause the pop star serenaded Russell Wilson for his 33rd -- and she brought cupcakes for the occasion too!

The NFL superstar had to hit the road for his cake day this year as the Seahawks are set to take on the Washington Football Team on Monday night -- but his talented wife made sure his big day got off on a positive note nonetheless.

Ciara sang him "Happy Birthday" in his hotel room ... and she even brought him out a grip of candle-lit sweet treats as well!!

Wilson clearly loved the gestures ... he leaned in for a big kiss from his wife, blew out the candles, and later wrote on his Instagram, "I love when u sing to daddy 😉🤣❤🙌"

It's an amazing gesture from Ciara -- and Seahawks fans are certainly hoping it brings some good juju to Wilson, who's struggled in his return from a finger injury.

Russ is 0-2 since coming back to the lineup -- and if the 'Hawks lose to the WFT on "MNF," their season might be over.