A statement issued Friday morning said Wynne, who represents the riding of Don Valley West, has scheduled an announcement for Monday in Toronto at 5:30 p.m.
Premier Dalton McGuinty confirmed Friday that Wynne will make a bid to replace him. He spoke just after she announced that she'd resigned her post — a prerequisite to running for the leadership.
"She's going to be a very strong candidate," McGuinty said in London, Ont.
"I'm very proud of all the contributions she's made to our party, to the government, but most importantly, to Ontarians in her various capacities as minister."
Wynne is expected to become the first candidate to officially declare her intention to seek the party leadership. The Liberals have scheduled a leadership convention for the weekend of Jan. 25 in Toronto.
McGuinty resigned last month and prorogued the legislature with his minority government under increasing pressure over questions about the closure of power plants west of Toronto.
Although no other Liberals have declared their intention to run, former Liberal cabinet minister Sandra Pupatello said last week she is "strongly leaning" toward launching a leadership bid. Toronto Centre MPP Glen Murray is another possible candidate. Former MP Gerard Kennedy, who narrowly lost to McGuinty in 1996, has also been mentioned.
So far the race has been notable for potential candidates who've declined to run, including Finance Minister Dwight Duncan, Energy Minister Chris Bentley and Scarborough Centre MPP Brad Duguid.
Former Liberal cabinet minister George Smitherman and Ottawa Centre MPP and party president Yasir Naqvi have also decided not to enter the race.
Wynne is perceived to be on the left of the Liberal party. She began her career in politics as a Toronto school trustee.
In her nine years at Queen's Park, she has also served as minister of education and transportation.