After months of campaigning, voters will finally take to the polls on Thursday June 23 to answer one question: "Should the United Kingdom remain a member of the European Union or leave the European Union?"
A short question, but with potentially huge ramifications.
Here is all you need to know on a monumental day:
What is the EU?
The EU is a group of 28 countries, which - according to the UK government's website - exists to promote economic security, peace and stability.
It operates an internal (or single) market which allows free movement of goods, capital, services and people between member states.
Why are we having an EU Referendum?
David Cameron promised to hold a referendum if his Conservative Party was successful at the General Election, after growing calls from the UK Independence Party (UKIP) and his own Conservative MPs.
UKIP had argued a referendum on EU membership hasn't been held since the UK was first elected in 1975.
Am I eligible to vote and where can I do it?
All British, Irish and Commonwealth citizens over the 18 who are residents in the UK - along with residents who have lived abroad for less than 15 years who are on the electoral register - are eligible to vote.
Citizens from other EU countries - including Ireland - will not be allowed to vote.
You don't need to take your poll card with you to vote. Polling stations will be open nationwide from 7am to 10pm on Thursday June 23.
If any voters have left it too late to return their postal vote by post, they can hand it in at their polling station.
What happens to my vote?
Your vote will be taken to a regional counting centre at 10pm. There are 12 regional centres in the UK.
Counting begins at 10pm and will last through the night. Sunderland has a reputation of being quick off the mark and are hoping to be first again.
The official declaration will be given at Manchester Town Hall.
Where can I find out more?
You can read and watch some of the highlights of our EU coverage over the last few weeks here: