David Ford MLA is stepping down as Alliance party leader.
Mr Ford's departure after 15 years as leader had been anticipated since he stood down after almost six years as Justice Minister in February.
He said the 15th anniversary of his succession as Alliance leader after Sean Neeson stood down was the most appropriate time "to step aside and pass the reins to a new generation of leadership for the party".
"Alliance has a well-established new Assembly team, which has hit the ground running by successfully submitting a number of private member's bills and continuing to provide the effective scrutiny of the Executive others have so far failed to do," he said.
"I am proud to represent the people of South Antrim, who most recently re-elected me for my fifth Assembly term in May, and I will continue to do that in Stormont and in the constituency. Whoever succeeds me as Alliance leader will be taking over a party on the rise. I am confident they will continue that upwards trend of growing the party, while providing leadership for everyone in our community."