MSP Stewart Stevenson has announced he will be retire next year after 20 years representing Banffshire and Buchan.
The 73-year-old, who has been a member of the SNP since 1961, will turn 75 by the 2021 election.
Elected to the constituency in 2001 – it later became Banffshire and Buchan Coast – Mr Stevenson has served as the SNP minister for transport, infrastructure and climate change and as minister for environment and climate change.
During his time in politics, he has also helped turn the 2009 Climate Change Bill into an act – something he regards as one of his biggest achievements, alongside securing the new prison in Peterhead.
Mr Stevenson said: “I’ve seen changes big and small.
“The community rallied around to keep the £15 million plus that prison jobs contribute annually in Peterhead.
“The partners of the prison staff fought in an exemplary fashion and I was happy to play my part.
“We saw the Chalmers Hospital rebuilt in Banff and significant investments made in Fraserburgh and Peterhead harbours.
“And 50% more people have signed up with NHS dentists in the area.”
As a minister and MSP, Mr Stevenson has been responsible for five parliamentary acts and for 132 pieces of other legislation.
He has participated in more than 40 elections and by-elections, made more than 820 parliamentary speeches, attended more than 1,000 parliamentary committees and held almost 1,200 constituent advice surgeries.
Mr Stevenson’s colleague, MSP Gillian Martin, became tearful as she learnt of his decision and paid tribute to his work.
“I’ll miss him in chambers – every speech he makes is a put down your pen and listen moment for many reasons,” Ms Martin said.
“But Stewart is more than that. He’s my pal and I’m so fond of him. He deserves to have a lovely retirement.
“From the moment I decided to put my hat in the ring to become an MSP, he has been an amazing source of advice, support and knowledge as well as kind, generous and fun.
“As convener of the environment, climate change and land reform committee, I’m not afraid to say I turn to him on many technical matters as his historic knowledge is incredible.
“I’ll really miss working alongside him.”
SNP MP Richard Thomson wished Mr Stevenson all the best for his retirement.
He said: “It’s going to be hard to imagine the Scottish Parliament without Stewart. Whether as a Minister or on the back-benches, he has been a true champion for the causes and people he was there to represent and could always be relied on to bring a knowledgeable and informed voice to debate.
“He’s been an exceptionally powerful voice for Banffshire and Buchan Coast over the years, as well as a stalwart colleague who has always been generous with his time and advice.”
But Mr Stevenson has no plans to leave politics behind completely.
Thanking his constituents for their “encouragement and engagement”, Mr Stevenson said: “My leaving parliament does not mean that I shall be leaving politics.
“Until Scotland can make its own decisions as a normal independent country, cooperating with friendly neighbours for moral causes, I’ll continue to lend my efforts wherever and whenever I can.
“I came into the SNP as a volunteer and expect to depart it, and eventually life itself, as one.”
In retirement, Mr Stevenson also plans to mentor others venturing into politics and continue his project looking at the Tee-Names of Nairn.
He said: “I know that there is a breadth of talent in the SNP ready to fight for the people of Banffshire and Buchan Coast constituency.
“To my successor as SNP candidate in 2021 – whoever they may be – you will have my full support.”