Karl Stefanovic's estranged wife Cassandra Thorburn ends her silence on their marriage breakdown.

Weeks after announcing their marriage split, Cassandra Thorburn has broken her silence about her 21-year partnership with Today host Karl Stefanovic.

According to news.com.au, the 44-year-old shared her thoughts about her estranged husband’s Channel 9 show had won the breakfast ratings top spot in a Facebook post on Monday night, beginning, “Apparently Today Show finally won a year.”

“This took a huge toll on my family and I, and I’m congratulating myself today for all the effort that went into making that happen,” the mum-of-three continued before sharing an all too familiar story of other women and partners out there.

“The suggestions, the story ideas, the constant counselling of questions for years," Thorburn said of the support she offered 42-year-old Stefanovic behind-the-scenes.

"I’m giving myself a pat on the back tonight, as I know many people will also know how much effort I put into it," Thorburn went on, adding that she was celebrating with a gift from Stefanovic's manager.

“Found a lovely tipple to cheers myself. Thanks for the red Sharon Finnigan SF Celebrity Management,” she said finally.

Thorburn's post is the first statement she has made since their split was announced a month ago.

Stefanovic is yet to comment publicly on the split, saying only that a good partner is worth "heaps" when co-host Lisa Wilkinson asked viewers “How much do you think your partner is worth?” during a recent segment.

Thorburn and Stefanovic have three children together, Jackson, 16, Ava, 11 and River, 10.