The Scottish Parliament will later vote to elect Scotland’s sixth first minister.
Newly elected SNP leader Humza Yousaf is almost certain to take the top job with a simple majority vote as the head of the party with the most MSPs.
He narrowly won the party leadership by just over 2,000 of the 50,490 votes.
The 37-year-old is the first Muslim to lead a major UK party and is set to become the first ethnic minority leader of a devolved government.
It is thought that Scottish Conservative leader Douglas Ross, Scottish Labour leader Anas Sarwar and Scottish Liberal democrat leader Alex Cole-Hamilton will all stand in the election.
However, none of the opposition leaders have any prospect of winning.
Mr Yousaf defeated rivals Finance Secretary Kate Forbes and Ash Regan in a leadership contest that exposed deep divisions within the party.
He failed to win a majority in the first round of voting, but won 52.1% of the votes after second preference votes from Ms Regan – who was eliminated after finishing third – were redistributed.
Ms Forbes came second with 47.9% of the votes when second preferences were included, with Mr Yousaf receiving 26,032 votes and Ms Forbes 23,890.
Both defeated candidates congratulated him on his success and urged voters to unite behind the party.
The SNP faced a fractious lead-up to Mr Yousaf’s successful election, with the party’s record in government facing criticism as well as a row over membership figures.
The Scottish Greens said its council had voted unanimously to continue to support the agreement with the SNP and for its MSPs to back Mr Yousaf in the vote to become the next first minister.
Scottish Greens co-leader Patrick Harvie told BBC Radio Scotland’s Drivetime programme that both Kate Forbes and Ash Regan made it clear in their campaigns that they would not keep the co-operative spirit in the agreement.
The new first minister can begin forming a cabinet after the election, with minister appointments expected to be made later this week.
The successful candidate will also face their inaugural First Minister’s Questions on Thursday.
Mr Yousaf is currently Scotland’s health secretary and he had been the clear favourite with the bookmakers during the contest.
He was seen as the “continuity candidate” following Nicola Sturgeon and was widely assumed to be her preferred successor.
He had by far the most endorsements from MSPs and MPs, including most of Ms Sturgeon’s inner circle.
However, his track record in government was criticised throughout the contest.
The health service faced record waiting times under his watch, although he has said that issue is not unique to Scotland.
Speaking after being confirmed as the new leader at Murrayfield Stadium in Edinburgh, Ms Yousaf said it would be “the greatest honour and privilege of my life” to be the next first minister.
He pledged to lead Scotland to independence by kickstarting a grassroots campaign.
After being voted leader of the Scottish National Party, we ask – who is Humza Yousaf?