MSPs like Pam Duncan-Glancy, Colin Smyth, Foysol Choudhury and John Mason have had their party whip removed and won’t return to Holyrood.
Others are leaving for health reasons, like the SNP’s Ruth Maguire, who is living with cancer.
Two former party leaders are standing down.
Richard Leonard, who led Scottish Labour between 2017 and 2021, will continue to campaign for a “more democratic, more equal, socialist society” from outside parliament.
Douglas Ross, who resigned as Conservative leader during the last Westminster election campaign, is seeking a return to the House of Commons.
He has enjoyed ruffling feathers during his time at Holyrood.
“Part of the role of an opposition politician is not to make it easy for the government.”
The Highlands and Islands MSP has spent 18 months as convener of Holyrood’s education committee, where he led scrutiny of Dundee University’s financial woes.
“I completely understand and accept that my style is not universally popular, but I think it has shown some people that you can have committees that are robust and agile to emerging issues.
“I think our committees here need to up their game a bit.”
Scottish Parliament Presiding Officer Alison Johnstone has also confirmed that she is among the third of MSPs who will not run for another term.
Many more could be voted out by the electorate on 7 May.
But Johnstone remains in office until her successor is elected and will be in the chair as the new cohort of MSPs are sworn in.