A post-Brexit trade deal has been agreed by negotiators from the UK and the European Union after months of talks and frantic last-minute wrangling.
The deal was secured on Christmas Eve, a week before current trading arrangements expire.
Taoiseach Micheál Martin welcomed the deal.
He tweeted: "#Brexit deal is very welcome after four long years of negotiations. Thanks to @vonderleyen &
@MichelBarnier & team. While we will miss the UK from the European Union, the fact that a deal is now in place means we can focus on how we manage good relationship in the years ahead."
A UK source said the deal delivered "everything that the British public was promised during the 2016 referendum".
UK prime minister Boris Johnson and European Commission president Ursula von der Leyen were in close contact over recent days to help get the deal over the line.
But negotiations led by the EU's Michel Barnier and the UK's Lord Frost continued throughout the day as final details were hammered out.
A Downing Street source said: "We have taken back control of our money, borders, laws, trade and our fishing waters.
"The deal is fantastic news for families and businesses in every part of the UK. We have signed the first free trade agreement based on zero tariffs and zero quotas that has ever been achieved with the EU.
"The deal is the biggest bilateral trade deal signed by either side, covering trade worth £668 billion in 2019."
The deal takes the UK out of the "lunar pull of the EU", no longer bound by Brussels' rules or the judgments of the European Court of Justice.
#Brexit deal is very welcome after four long years of negotiations. Thanks to @vonderleyen & @MichelBarnier & team. While we will miss the UK from the European Union, the fact that a deal is now in place means we can focus on how we manage good relationship in the years ahead.— Micheál Martin (@MichealMartinTD) December 24, 2020
"All of our key red lines about returning sovereignty have been achieved," the source said.
"It means that we will have full political and economic independence on January 1 2021."
Echoing the prime minister's election slogan, the source said "we have got Brexit done".
European Commission chief Mrs von der Leyen said: "We have finally found an agreement.
"It was a long and winding road, but we have got a good deal to show for it.
"It is fair, it is a balanced deal, and it is the right and responsible thing to do for both sides."