Jeffrey Donaldson will be replaced at the Northern Ireland Assembly, the DUP has confirmed.
Lisburn councillor Paul Givan takes over as MLA for Lagan Valley following the MP's resignation.
The party has promised that its MPs would give up their Assembly positions.
Mr Givan is a former special adviser in the Department of the Environment.
"I am delighted to have been chosen for this position and will seek to serve the constituents of Lagan Valley to the best of my ability, putting them first in all that I will do at the Assembly.
"I am joining a strong DUP team in Stormont that is delivering for the people of Northern Ireland."