Scottish Labour: A brief history of leaders since 1999
The party will now have to choose its ninth leader since devolution began.
Since devolution, Scottish Labour has burned through more leaders than the SNP and the Scottish Conservatives combined.
Kezia Dugdale's abrupt departure from the position, announced late on Tuesday, leaves the party facing its sixth leadership election in a decade.
Members, MSPs, MPs and affiliated groups will now need to choose their ninth leader since Holyrood opened for business in 1999.
By comparison, the SNP has been led by Alex Salmond (twice), John Swinney and Nicola Sturgeon, while the Tories have had David McLetchie, Annabel Goldie and Ruth Davidson.
The Scottish Liberal Democrats, for their part, have had four leaders, while the Scottish Greens have had seven conveners or co-conveners.
So let's take a look at Scottish Labour's various leaders down the years.
Kezia Dugdale: 2015-2017
The most recent incumbent ran for the leadership against Ken Macintosh at a particularly grim moment for the party, and won handily.
She had already been deputy leader and leader at Holyrood during MP Jim Murphy's tenure, which ended with Labour losing all of its Scottish seats at Westminster bar one.
Dugdale then endured watching her party get pushed to third place in the 2016 Scottish Parliament election to Ruth Davidson's resurgent Conservatives.
She enjoyed a surprise bounce in June's general election, however, clawing back six seats from the SNP to bring the party's total MPs to seven.
Beyond that, she is credited with getting greater autonomy and democratic representation for the Scottish party on a UK level as well as helping to rebuild it.
Jim Murphy: 2014-2015
Coming in at the tail end of 2014 and gone by the next summer, Jim Murphy's six-month tenure is the shortest on record against several contenders.
Then East Renfrewshire's MP, he spearheaded a change to Scottish Labour's Clause IV dedicating the party to working "for the patriotic interest of the people of Scotland".
This reorientation failed to put the brakes on plummeting polling numbers or the SNP's rising star, eventually leading to a crushing defeat in the 2015 general election.
Labour lost 40 seats in Scotland and were reduced to a solitary MP north of the border (and it wasn't Jim Murphy).
The SNP, meanwhile, swept the board, winning 56 out of 59 seats.
Murphy resigned a month later, saying: "The most difficult thing for any party to realise after a defeat is that it has to change."
Johann Lamont: 2011-2014
Lamont had, by party standards, a fairly lengthy time in the leader's office, serving a respectable two years and ten months.
The MSP took on Alex Salmond during his time as First Minister and Labour bested the SNP in a number of by-elections as well as handily retaining Glasgow City Council in 2012.
A figurehead of the Better Together campaign in the run-up to the independence referendum, Lamont took on Nicola Sturgeon in a televised debate in 2014.
She raised her opponent's ire by describing nationalism as a "virus".
But she was to resign after the referendum with an explosive statement accusing UK Labour HQ of treating the party in Scotland as a "branch office" and calling for more autonomy.
Iain Gray: 2008-2011
Reaching the heady heights of three years and three months in post (albeit the final seven in a caretaker role), Iain Gray is the longest serving party leader post-devolution bar Jack McConnell.
It seemed at one point, like McConnell, that Gray would become a Labour First Minister, with his party ascendant in the polls for much of the time against Salmond's minority SNP administration.
In the final weeks of the 2011 Scottish Parliament election that lead was cut down and eventually reversed, and his party lost a swathe of seats as the SNP took a Holyrood majority for the first and only time.
He was stung by a couple of campaign blunders, including trying to hide from protesters in a Subway shop in Glasgow and a bizarre dispute with Salmond over which leader ran away from the other when they visited the same supermarket in Ardrossan.
And then there was this moment from a leaders' debate.
Wendy Alexander: 2007-2008
Elected to the position unopposed, Wendy Alexander was the first to serve the party as leader of the opposition after it had spent eight years in coalition with the Lib Dems.
She called for reform and vowed to "reconnect Scottish Labour with its electorate", and helped set up the cross-party Calman Commission to review devolution.
Alexander also boldly suggested she would be willing to support a referendum on Scottish independence with the words: "Bring it on." One problem was that then-Labour PM Gordon Brown did not seem to agree.
She quit the role due to issues around donations her campaign for the leadership had taken, although authorities ultimately took no action against her.
Jack McConnell: 2001-2007
Scottish Labour's longest serving First Minister and now a lord, McConnell took over from Henry McLeish in 2001 and led his party to victory against John Swinney's SNP in the 2003 Holyrood election.
In his time as First Minister, he was an early backer of Glasgow's Commonwealth Games bid and oversaw the ban on smoking in public places, making Scotland the first place in the UK to implement the policy.
The return of Alex Salmond to the SNP leadership buoyed the party, and after eight years in power, Labour lost to the SNP in the 2007 Scottish Parliament election by the slimmest of margins - one seat.
McConnell was re-elected as the MSP for Motherwell and Wishaw but announced he would resign as Scottish Labour leader three months later.
Henry McLeish: 2000-2001
After the death of Donald Dewar, Henry McLeish - Dewar's right-hand man in helping secure devolution - defeated McConnell to become Scottish Labour leader and Scotland's First Minister.
In his short year in the role, McLeish took on numerous official trips, memorably going to meet the Pope and also visiting the United States.
He also sought to boost the competitiveness of Scottish industry.
McLeish's time as First Minister was embroiled in scandal after it emerged he received £36,000 from sub-letting his constituency office in Fife during his time as an MP. He tendered his resignation to the Queen.
Donald Dewar: 1999-2000
Remembered as the key architect of the devolution settlement, he helped produce the Scotland Act upon which Holyrood would be based.
Dewar also campaigned vigorously for a Yes-Yes vote to win a Scottish Parliament in the 1997 referendum.
He was elected to the chamber in its first election in 1999 as leader of Scottish Labour and became the country's inaugural first minister.
Dewar died, aged 63, on October 10, 2000, died after suffering a brain haemorrhage.
A statue was built two years later to commemorate him on Buchanan Street in Glasgow.