LOS ANGELES • Arnold Schwarzenegger has many past and present roles - father, action superstar, bodybuilder, businessman and former governor of California.

And the 73-year-old has taken on a new role - that of a grandfather.

His daughter Katherine, who is an author, announced on social media on Monday that she has given birth to a baby girl.

The 30-year-old, who is married to Hollywood actor Chris Pratt, wrote: "We are beyond thrilled to announce the birth of our daughter Lyla Maria Schwarzenegger Pratt."

She posted a photo of herself and Pratt holding the baby's hand.

Pratt, who is known for his roles in the Guardians Of The Galaxy movies (2014, 2017) and the Jurassic World movies (2015, 2018), shared the same post on Instagram, adding that "both mum and baby are doing great".

Schwarzenegger began dating Pratt, 41, in June 2018 after he divorced actress Anna Faris.

They got engaged in January last year and tied the knot in June the same year.

It was reported in April this year that they would be expecting their first child together. Pratt has an eight-year-old son with Faris, 43.

Katherine Schwarzenegger, who in March launched her fourth book, The Gift Of Forgiveness: Inspiring Stories From Those Who Have Overcome The Unforgivable, is the eldest child of Arnold Schwarzenegger.

The Terminator (1984 to 2019) actor has so far not commented publicly on the birth of his first grandchild, but was seen riding a motorcycle a la his character in The Terminator movies in Los Angeles, which the Daily Mail described as a "victory lap".

He has three other children with his former wife, television journalist Maria Shriver.

Shriver, 64, filed for divorce in 2011 following Schwarzenegger's admission that he fathered a child with the family's housekeeper.