Former Alliance party deputy leader Eileen Bell will be the speaker at the Northern Ireland Assembly when it is recalled.
Eileen Bell will assume the role of assembly speaker
Mrs Bell was named as presiding officer by the NIO on Monday.
The North Down MLA announced in December she would not stand in the next assembly election.
It is thought the appointment is for the first session of the assembly on 15 May when members can decide to keep Mrs Bell as speaker or choose someone else.
Alliance leader David Ford said it would have been "appropriate and good manners" for him to have been informed in advance of the decision.
Previously Mrs Bell took part in the Stormont Commission which managed the Stormont Estates in the last assembly.
Mrs Bell, the first Catholic and the first woman to hold the post, said she was looking forward to her new role.
"I was delighted to be asked by the secretary of state to take up the post of presiding officer of the assembly.
"I am honoured to accept this post and I look forward to the challenges when the assembly meets on 15 May," she said
Northern Ireland Secretary Peter Hain said he thought she would prove to be a good choice as speaker.
"Eileen is hugely respected across the political and community divide in Northern Ireland," he said.
"She gets on with everyone and brings a wealth of experience to the post.
"I am very pleased that she has agreed to take up this very important post of presiding officer. I am sure she will do a good job."
Lord Alderdice, the assembly's last speaker, retired from the post in February 2004 citing the demands of his role on the Independent Monitoring Commission as the main reason for his decision.
He was appointed to the position in July 1998.
The assembly has been suspended since October 2002 following allegations of a republican spy ring at the Northern Ireland Office.