A Westminster by-election triggered by the resignation of Sinn Féin's Barry McElduff will be held on Thursday 3rd May.
He resigned his position in January amid controversy over a video he posted on Twitter.
The brief video showed him with a loaf of Kingsmill bread on his head, on the anniversary of the Kingsmill massacre.
He deleted the post soon after, claiming he did not realise the connection.
The massacre on January 5th 1976 saw a van carrying group of textile workers pulled over by men disguised as British soldiers.
The workers were lined up and asked their religion before the gunmen opened fire.
Ten men were killed.
Sinn Féin has announced 26-year-old solicitor Órfhlaith Begley will contest the seat for their party.
On her nomination, she said: "I want a modern and inclusive Ireland. An Ireland in which political persuasion, gender, sexual orientation, religion, or skin colour make no difference as to how a citizen is treated.
"We can achieve all of that and much more when we have determination and energy and when we work closely with the citizens who are now taking these campaigns forward."
The date also coincides with local government elections in some parts of England.
British, EU and Commonwealth citizens are entitled to vote in UK local elections.