Nationalist MSP Margaret Ewing has announced that she is to stand down at the Holyrood elections in 2007.
Margaret Ewing has suffered from ill-health
Mrs Ewing, 59, has represented the Moray area in Westminster and Holyrood for the last 20 years.
She is married to Fergus, MSP for Inverness East and son of Nationalist stalwart Winnie, who will retire as party president in September.
Mr Ewing has confirmed that he will be standing for re-election. Party leaders have paid tribute to his wife.
Mrs Ewing said: "I'd always decided that I would retire when I reached retirement age.
"Many of my good girlfriends of the same age have already retired and seem to be having the life of Riley.
"I want to be young enough and healthy enough to enjoy my retirement."
Mrs Ewing was born in rural Lanarkshire and trained for the teaching profession at Glasgow University.
She joined the SNP in 1966 and entered parliament as MP for East Dunbartonshire, winning with a majority of just 22 in 1974.
She lost the seat five years later and, after failing to get into parliament in 1983 in Strathkelvin and Bearsden, she won the Moray seat from the Tories in 1987.
Mrs Ewing became the SNP's parliamentary leader at Westminster and ran for party leadership three years later but was defeated by Alex Salmond.
In 1999 she became MSP for Moray and stood down from her Westminster seat in 2001 to concentrate on Holyrood.
In 2002, Mrs Ewing underwent treatment for breast cancer at Edinburgh's Western General Hospital but returned to Holyrood later that year.
Paying tribute to her, Mr Salmond said: "Margaret's contribution to the SNP and Scottish political life has been immense.
"From winning a central belt seat from the Conservatives for the SNP at the general election in 1974 to her tireless campaigning on issues such as the warm homes campaign, Margaret has been an inspiration as a political colleague.
"Her political skill and experience will be greatly missed by the SNP at a national level. I wish her well in her retirement from frontline politics, but look forward to the many ways in which she will contribute to Scotland's cause in future."
The party's Holyrood leader, Nicola Sturgeon, said: "Margaret has been an invaluable colleague since our election to the Scottish Parliament in 1999.
"Her long experience as a parliamentarian has been an enormous asset to the SNP group at Holyrood and her retirement will leave a gap that will be hard to fill.
"Her record of fighting for the best interests of her constituents is second to none, and they too will miss the benefit of her tenacious approach to representing the people of Moray."