Premier Daniel Andrews paid tribute on Wednesday night to a tireless campaigner who stood up for the safety of women and children; who knew no fear and tolerated no prejudice.

"She was a person of conviction, of character, of extraordinary composure," Mr Andrews said.

"Those qualities – combined with an intellect and instinct that's among the sharpest I've known – made her someone who can never be replaced. Not in our Government. Not in our movement. Not ever."

Ms Richardson's family paid tribute to a gutsy campaigner who had a significant impact at a local, state and national level.

"She was an unwavering advocate on behalf of victim-survivors and every Victorian touched by the tragedy of family violence," their statement said.

Ms Richardson was first elected to Parliament in 2006.

She successfully battled cancer in 2013 and returned to become the nation's first minister for the prevention of family violence.

Her death comes just one day after she announced she was taking more time off after being diagnosed with multiple tumours.

She said she had intended to return to work part-time, but her recovery was not progressing as planned.

The 50-year-old is survived by two children, Marcus and Catherine, and husband, Stephen.

"She achieved so much for victims in a short space of time," her family's statement said.

Ms Richardson oversaw the Royal Commission into Family Violence, championed family violence leave for public sector workers and developed the state's first gender-equality strategy, which the nation is now working to emulate.

She shared her own family's experience with domestic violence on ABC's Australian Story - a move which her family said "took guts".

"Her strength and insight ... touched the lives of many people and allowed them a glimpse of why she was such a fearless champion for victim-survivors," the family said.

"Fiona had unfinished business. She wanted violence in the home to stop and she knew for that to happen it would take dedication and leadership over the course of a generation."

Mr Andrews said Ms Richardson exposed Victoria's "dark and silent" tragedy of family violence through the royal commission.

"The 2000 pages of that commission's final report are her greatest legacy to public life," he said.

"Victoria has a different system now. Our state will never be the same. Lives have been saved. And I know who to thank."

The Premier said Ms Richardson also paved the way for other women to enter parliament.

"Before she had even stepped foot in Parliament, she had busted the party's sexist back rooms and committees wide open," he said. 

"She made things that much easier and fairer for the next generation of Labor women. And for the one after that."

Tribute flowed from both sides of politics on Wednesday night.

Victorian Opposition Leader Matthew Guy said: "Vale Fiona Richardson MP. The sadness at Spring Street will be immense. To her family, friends, colleagues, my thoughts, sympathy and love".

Federal Opposition Leader Bill Shorten described Ms Richardson as a dear friend to him and his wife, Chloe. 

"For those of us privileged to know her, she was a steely-eyed legend," he said.

"She was as tough as they make them, persevering through such adversity and accomplishing so much, especially when it came to tackling the scourge of family violence." 

Mr Shorten said his friend was a fighter until the end, "strong and resilient". 

"This is a terrible shock - I thought we had more time. Chloe and I will miss Fiona immensely. We ask Victorians to keep Stephen and their children in their hearts."  

Campaigner against domestic violence Rosie Batty said she was devastated by her friend's passing.

"Huge support to me during my journey and for all victims," she said. "Thoughts with family, staff and all"

Government minister Philip Dalidakis praised Ms Richardson as "tenacious and principled".

"She was a very private person and yet understood the power of publicly talking about what would have been a very painful recount of her family story and her experience with family violence," he said.

"Her legacy will continue to live on. We are better for her living and poorer for her passing."

Mr Dalidakis credited Ms Richardson with encouraging him in his career. 

"She was a mentor of mine and played a large part in me being a member of parliament and indeed joining the ministry," he said. 

- with Ben Preiss, Debbie Cuthbertson, Melissa Cunningham