Olivia Culpo's got a bun in the oven -- the model and Christian McCaffrey are expecting their first child together!!

Waiting for your permission to load the Instagram Media.

The 2020 Sports Illustrated Swimsuit cover girl broke the news on Instagram Monday morning ... sharing a stunning pregnancy photo shoot with the caption, "next chapter, motherhood 🤍." She also shared a video showing off her bump in a white dress as she walked holding hands and kissing Christian.

She was recently spotted hitting a café in Encino... and her pregnant belly was visible through her jacket.

No word on whether it's a future Miss Universe or NFL running back ... but Culpo is clearly a few months along.

It seems like OC was trying her best to avoid bringing attention to her growing tummy while in New Orleans for the Super Bowl ... electing for oversized jackets and dark colors.

As we previously reported, Culpo and the NFL superstar tied the knot at a lavish ceremony in Rhode Island back in June ... with their closest family and friends in attendance.

The two have been together since 2019 ... and after years of dating, CMC got on one knee and proposed in 2023.

Guess "first comes love, then comes marriage, then comes the baby in the baby carriage" still rings true to this day!!