Brittany Mahomes is back in the gym only months after giving birth to her third child ... and she's proud of her gains.

The wife of Kansas City Chiefs quarterback Patrick Mahomes shared a mirror selfie Wednesday during a workout ... and she's looking super fit postpartum.

Brittany showed off her body in a pink sports bra, matching leggings and matching shoes ... playfully asking her followers, "How much pink is too much?"

It's hard to tell Brittany is only two months removed from giving birth ... and it looks like she's been working hard in the gym.

Brittany gave birth January 12 to a baby girl named Golden Raye Mahomes and she was mostly covered up in public appearances during the NFL playoffs.

Of course, a lot of those games were outdoors at chilly Arrowhead Stadium in Kansas City.

Brittany and Patrick now have three kids together ... and while it may be the offseason for him, she's hard at work hitting the weights.