The DUP has revealed that Derry councillor Maurice Devenney will replace William Hay as MLA for Foyle.
Former Assembly Speaker Hay resigned his seat earlier this month due to health reasons.
Mr Devenney has been a Derry city councillor since 2005 and was Mayor of the city in 2011-2012.
First Minister Peter Robinson said he was “delighted” to welcome the party’s newest MLA.
“When William Hay decided to step down from the Assembly, the Democratic Unionist Party lost a dedicated and hard-working constituency representative,” he said.
“I am delighted, however, that the DUP will continue to be represented by someone well known to the people of Londonderry and with a track record of delivering for the community.
“Maurice will further strengthen the DUP team in the Assembly and will make a valuable contribution to debates and in the committees he will serve on,” he said.
“He joins the Assembly on a day it debates the most significant Private Members Bill ever brought forward at Stormont with Lord Morrow’s Human Trafficking Bill reaching consideration stage in the chamber.”
Mr Devenney signed the members register to officially take up his seat on Monday.