DOWNLOAD OUR APPS
Baraclough, 49, has served as the country's Under-21 boss for the past three years.
His promotion to the senior role was confirmed on Sunday (AEST) by the Irish Football Association.
O'Neill joined EFL Championship side Stoke City in November 2019 after eight years in charge of Northern Ireland.
He initially combined the position with the national team job before stepping down in April this year.
O'Neill had hoped to lead the team into the UEFA Euro 2020 play-offs, but decided against carrying on when it was delayed because of the coronavirus pandemic.
Baraclough will instead have that task, with Northern Ireland to play Bosnia-Herzegovina in the semi-finals on 8 October.
The former Motherwell and Scunthorpe United manager's first game in charge will come before that, with an away fixture against Romania in the UEFA Nations League on 4 September.