Voters in Northern Ireland are getting the opportunity to decide who should represent them in the House of Commons.
Some 102 candidates are competing in the general election for 18 Westminster seats allocated to Northern Ireland.
Polling stations opened at 07:00 GMT on Thursday and will close at 22:00, with the results expected to be finalised on Friday morning.
A total of 1,293,971 people are eligible to vote in Northern Ireland.
- Increase in number of voters on electoral register
- A really simple guide to the election
Chief electoral officer Virginia McVea said staff had been in from 05:00 GMT, making sure “all the boxes are in the right place and the staff are where they’re meant to be”.
She added: “This is an extremely busy day with over 1,300 polling stations and 5,000 staff deployed until the early hours of tomorrow morning.”
Ms McVea said in the 2017 general election the first Northern Ireland results were known at about 01:00.
“Hopefully the weather will stay not too bad, a lot of this is about getting the ballot boxes transported to the various count centres round Northern Ireland.”
Do I mark the ballot paper with an X or 1,2,3?
A UK general election operates on a first-past-the-post system.
Voters should mark the ballot paper with a single X next to their candidate of choice.
The Single Transferable Vote system is only used for assembly, local council and European elections in Northern Ireland.
Can I vote in the election?
Voters have to be aged at least 18 and on the electoral register to vote in Northern Ireland.
The deadline to register for the election has passed so anyone who has not already registered cannot take part.
The Electoral Office said there has been a rise in the number of eligible voters in each of the 18 constituencies.
Do I need to bring ID to the polling station?
Voters in Northern Ireland must bring photo ID to the polling station. The polling card received through the post is for information purposes only and is not acceptable ID for voting purposes.
The following ID documents are accepted:
- A UK, Irish or EEA driving licence (photographic part; provisional accepted)
- A UK, Irish or EU passport
- An Electoral Identity Card
- A Translink Senior SmartPass
- A Translink 60+ SmartPass
- A Translink War Disabled SmartPass
- A Translink Blind Person’s SmartPass
How can I follow the results?
Counting in the election will begin as soon as the polls close at 22:00 GMT, and will continue overnight with the final results expected on Friday morning.
BBC News NI will cover the latest election results and analysis on its website, mobile app and on Facebook and Twitter throughout the night, from 21:45.
Television coverage will begin on BBC One Northern Ireland at 21:55 on Thursday.
There will also be a special overnight election programme on BBC Radio Ulster from 21:55 that will continue until Friday morning, when Good Morning Ulster will have further reaction and analysis of the results.