Hilary Duff is a new mum.

The 31-year-old actress and singer and her boyfriend Matthew Koma welcomed Banks Violet Bair on Thursday (25Oct18), and the proud parents have now taken to social media to share their happy news with fans and followers.

"Banks Violet Bair this little bit has fully stolen our hearts!" So Yesterday singer Duff wrote beneath a photo of mum and dad cuddling the newborn. "She joined our world at home on Thursday afternoon and is absolute magic."

Matthew added: "We welcome a beautiful daughter, little sister, and best friend for life. Could not possibly be more grateful for our growing family... Cloud ten."

The couple teased the baby’s arrival earlier on Monday (29Oct18) when Koma took to Instagram to share a sweet video of tiny baby feet, hours after Duff referred to him as "dad" in a post.

Hilary is also mum to six-year-old Luca, her son with ex-husband Mike Comrie, but this is music producer Koma's first child.

They announced the baby news over the summer (Jun18), by posting an Instagram shot of the mum-to-be showing off her baby belly for the first time: "@matthewkoma and I made a little princess of our own and we couldn’t be more excited!!!!!!" she wrote.

Regular posts suggested Hilary had a great pregnancy, but she was ready to give birth, joking her second child was outstaying her welcome.

She took to her Instagram Story timeline last week (23Oct18) to share a snap of herself in bed, looking down at her bare belly, encouraging her daughter to make her grand entrance.

"Yo... your hotel stay is up little girl," the mother-to-be captioned the post.

It's not clear exactly when Hilary was due, but she recently revealed she was attempting to induce labour by eating a famous salad known for sending women into the delivery room.

The Younger star uploaded a snap of the healthy greens, which included romaine lettuce, watercress, walnuts, and Gorgonzola cheese in a balsamic vinaigrette on 14 October (18).

"This salad is supposed to make you go into labor...," she wrote.