Premier Jacinta Allan will deliver a formal apology to care leavers on behalf of the government for historical abuse and neglect.
Between 1928 and 1990, an estimated 90,000 Victorian children were placed into institutions such as orphanages, children's homes and missions run by the state or religious groups.
Thousands suffered abuse and neglect.
Ms Allan said the state owed them an apology for the life-long consequences that stemmed from the harm they faced as children, with many experiencing poverty, homelessness and mental health issues as adults.
"They've waited a long time for this day," Ms Allan told reporters outside parliament.
"Many of them who have carried that trauma of that abuse and neglect have also worked so incredibly hard to make today happen.
"Today is about honouring their strength and reliance and resistance."
Before 1990, while in institutional care, thousands of Victorian children experienced abuse and neglect.— Jacinta Allan (@JacintaAllanMP) It's important we acknowledge that hurt.On Thursday in Parliament, that's what we'll be doing.Live stream: https://t.co/ZnquIwKKQcFebruary 6, 2024
More than 200 guests have been invited to parliament for the event.
Those who missed out can watch the apology online from 11.30am or at live sites in Geelong, Ballarat and Sale with counsellors on hand.
A redress scheme for those who suffered abuse or neglect in state care over the six-decade span is still to be rolled out.
Ms Allan said the government would consult with care leavers and their advocates on the design of the scheme.
"It's co-designed with the people who have had that lived experience because we want to get it right," she said.
"That work will start soon and it will be completed over the course of 2024."
The apology to care leavers was scheduled to be delivered on November 29 but was pushed back to give victims and advocates more time to prepare.
Former premier Steve Bracks issued a formal apology to former wards of the state for institutional abuse and neglect following the recommendation of a 2004 federal report.
In 2018, then-prime minister Scott Morrison delivered a national apology to institutional sex abuse victims and survivors after a federal royal commission.
Former premier Daniel Andrews pledged to deliver a formal apology in parliament to survivors of all forms of abuse in institutional settings if Labor was re-elected in 2022, tying the two previous apologies together.
A separate apology has also been promised by the state government to students abused at Beaumaris Primary School in Melbourne's southeast from the 1960s until 1999.