Member for Flinders Peter Treloar has announced he will not seek re-election at the next state election.
With nominations now open for incumbent Liberal MPs, Mr Treloar has advised the Premier and Liberal Party state director of his decision to not contest the election in March 2022.
Mr Treloar was first elected in 2010 and was returned at the 2014 and 2018 elections.
"I will have had the honour and privilege of representing the electorate of Flinders for three terms, a total of 12 years in the state parliament," he said.
"I've thoroughly enjoyed my time serving the people of Eyre Peninsula, and am grateful for the confidence and support given me."
Mr Treloar had been appointed to various parliamentary roles in both opposition and government, and is currently deputy speaker and chair of committees in the Marshall Liberal Government.
He said he appreciated the support of his family and staff over the past decade.
"I'd particularly like to thank my family. Being a Member of Parliament is a job like no other, and I greatly appreciate the support my wife Annette, our four children and their partners have given me over the past 12 years," Mr Treloar said.
"I also want to take this opportunity to thank my staff who have worked tirelessly with me over this time to ensure our electorate offices at Port Lincoln and Ceduna provide service to constituents."
Mr Treloar said he intended to continue living on his family farm at Edillilie and was looking forward to once again being actively involved in farming, as well as spending more time with his family.
Premier Steven Marshall said Mr Treloar has served his electorate with distinction.
"As the Member for Flinders, Peter has been a proud advocate for the Eyre Peninsula and regional South Australia more broadly, always fighting for the interests of the agricultural, fishing and tourism sectors with passion and integrity," he said.
"I wish Peter and his lovely wife Annette well in their next chapter - I'm sure Annette will be very pleased to have Peter back on family farm at Edillilie on a more permanent basis."
The Electoral Districts Boundaries Commission recently released its final redistribution report which outlined electoral district boundaries for the next election cycle, with Flinders to gain the Kimba and Franklin Harbour district councils as well as Maralinga-Tjatjura from the Giles electorate.