Toni Collette and her husband David Galafassi are divorcing after nearly 20 years of marriage.

The 'About A Boy' actress took to Instagram to announce the pair - who married in January 2003 - are "united" in their decision to go their separate ways, and says they will "continue to thrive as a family", because their two children are of "paramount importance" to them.

Toni - who shares daughter Sage, 14, and son Arlo, 11, with David – posted a picture of a flower arrangement that reads "peace and love", and she added the caption: "It is with grace and gratitude that we announce we are divorcing.

"We’re united in our decision and part with continuing respect and care for each other. Our kids are of paramount importance to us and we will continue to thrive as a family, albeit a different shape. We’re thankful for the space and love you grant us as we evolve and move through this transition peacefully.

Big thanks.

Toni Collette and David Galafassi"

The post came after the 'Knives Out' star shared a quote on her Instagram Stories, which read: "No matter what your current circumstances are, if you can imagine something better for yourself, you can create it."

Australian actress Toni returned to her dormant Instagram account just five days ago, and posted a picture of herself holding a drink.

She wrote in the caption: "I’m back. Hello world. I love you"

David was drummer of the band Gelbison when they first met, but he later joined his wife's group Toni Collette and the Finish.

Toni wrote the 11 tracks of the band's only album, 'Beautiful Awkward Pictures', which dropped in 2006, and they toured Australia in 2006 and 2007.