Alliance MLA Patrick Brown has resigned with immediate effect for personal reasons.
The South Down representative was elected to the Stormont Assembly in 2022.
He previously served as a councillor in Down.
On Tuesday an Alliance Party spokesman said: “It is with regret we announce Patrick’s immediate resignation due to personal reasons.”
“We thank him for his service, which saw him help Alliance make an historic breakthrough in South Down at the Assembly, and wish him well in his future endeavours.”
Mr Brown said he will continue to support the Alliance Party and whoever replaces him in his MLA role.
He also thanked those who supported him.
“This May, I will have been an elected representative for 10 years and feel the time is right to step aside for personal reasons,” he said.
“I am proud of the work I have done since being elected, including supporting those impacted by flooding, campaigning on environmental and animal welfare issues, and my work on the Windsor Framework and Infrastructure Committees.
“Alliance continues to have my support, as will whoever is co-opted by the party to fill the position of South Down MLA.”
