Paris Hilton is "so excited" about Britney Spears' pregnancy news.

The Toxic hitmaker announced via Instagram on Monday that she is expecting a baby with her partner Sam Asghari.

Britney was quickly inundated with supportive messages, with Paris writing, "Congratulations sis!! I'm so excited for you!! Love you!!!"

Other celebrities to comment included Iggy Azalea, Jenni 'JWoww' Farley, and Tess Holliday.

In addition, Sam took to social media to share a photo of two lions and a lion cub. In the accompanying caption, he shared his joy over becoming a father.

"Marriage and kids are a natural part of a strong relationship filled with love and respect. Fatherhood is something i have always looked forward to and i don't take lightly. It is the most important job i will ever do (sic)," he wrote.

The pair got engaged last September, shortly before Britney's conservatorship was terminated. In recent Instagram posts, the singer has referred to him as her "husband", sparking speculation that they have married in secret.

Britney shares sons Sean Preston, 16, and Jayden James, 15, with ex-husband Kevin Federline.

Reacting to the news, lawyer Mark Vincent Kaplan told NBC News that Kevin is very happy for the 40-year-old star.

"He wishes her the best for a happy, healthy pregnancy and congratulates her and Sam Asghari as they plan for the excitement of parenthood together," he added.