The 57-year-old Australian was awarded for her risque role in the erotic Babygirl, where she plays a hard-nosed CEO who jeopardises both her career and her family by having a toxic affair with a young, manipulative intern played by Harris Dickinson.

Speaking to the audience at the festival on Saturday night via a note read out by Babygirl director Halina Reijn, Kidman said her "heart is broken".

It read: "Today I arrived in Venice to find out shortly after, that my beautiful, brave mother Janelle Ann Kidman has just passed.

"I am in shock and I have to go to my family, but this award is for her, she shaped me, she guided me, and she made me.

"I am beyond grateful that I get to say her name to all of you through Halina, the collision of life and art is heart-breaking, and my heart is broken.

"We love you all."

The 81st edition of the film festival closed on Saturday, with Pedro Almodovar's English-language debut The Room Next Door winning the festival's most prestigious prize, the Golden Lion, which is awarded for best film.

Starring Tilda Swinton and Julianne Moore, the film received an 18-minute standing ovation when it premiered at Venice earlier in the week - one of the longest in recent memory.

With AAP.