The replacement for the retiring David Ford will be Stormont's first openly gay MLA, the Alliance party has said.
Newtownabbey Councillor John Blair has been selected by the party as the new MLA for South Antrim.
He represents Glengormley on Antrim and Newtownabbey Borough Council and was previously a Deputy Mayor.
The 52-year-old, who will resign his council position, said he was looking forward to tackling the issues facing South Antrim, saying he was "honoured and delighted" to take over from David Ford.
"His leadership and vision has helped grow the party both in the constituency and wider,” he said.
“I will be looking to build on my previous work as councillor and provide a strong Alliance voice for local people, here in South Antrim and also in the Assembly. We are a growing party and we are already hitting the ground running ahead here of next year’s council elections.
"Since deciding to run for the MLA seat, I have received support and encouragement from right across the community, showing the progressive and positive alternative Alliance represents."
Mr Blair said he wanted to carry out all the duties of an MLA saying it was "vital" the Secretary of State calls all-party talks with an independent mediator immediately, "so we can all get back to Stormont and do the job people want us to do".
“I look forward to doing just that, while representing all the people of South Antrim and providing a strong voice for them, whether rural or urban," he said.