Former Senator Rob Simms will be the lead candidate for the Greens in the upper house at the next South Australian election in 2022.
Mr Simms served in the Senate from September 2015, when he filled a casual vacancy, until he lost his seat at the March 2016 federal election.
He is currently a serving member of the City of Adelaide council.
He will now take top spot on the Legislative Council ticket for the Greens at the next state poll, his position confirmed by a ballot of party members.
The move follows the decision by sitting upper house MP Mark Parnell not to seek re-election for a third, eight-year term.
Mr Simms said he felt honoured to be chosen by party members
"As our state grapples with the climate crisis and growing inequality, the Greens' vision for a fairer and more sustainable South Australia has never been more important," he said.
"I look forward to campaigning with Green members and supporters in the year ahead."
Mr Parnell said Mr Simms would be a great addition to the parliament.
"In his brief time in the Senate and during his time on Adelaide City Council, Robert Simms has shown that he has the skills, enthusiasm, temperament and commitment to represent all South Australians," he said.
