European Commission and European Council presidents Ursula von der Leyen and Charles Michel have signed the Withdrawal Agreement formally confirming Brexit, which will now be delivered to prime minister Boris Johnson to receive his signature.
The Queen has already approved the document, with the European Parliament expected to vote in its favour next week.
The document paves the way for the UK's departure from the bloc on January 31, ending 46 years as a member nation.
Prime minister Boris Johnson hailed the signing off of the Withdrawal Agreement as “crossing the Brexit finish line”.
He added: "Now we can put the rancour and division of the past three years behind us and focus on delivering a bright, exciting future - with better hospitals and schools, safer streets and opportunity spread to every corner of our country.”
Chief EU negotiator Michel Barnier was present alongside von der Leyen and Michel during the signing ceremony.
The UK will continue to abide by EU rules during the Brexit transition period which will run until December 31. During these 11 months, the UK and EU will seek to agree a deal on their future relationship.
Johnson and his cabinet are confident of agreeing a comprehensive deal by the end of the year, despite concerns from von der Leyen and other EU officials that the window may be too short.