Article 50, which will give Theresa May the power to begin the process of leaving the EU, has been granted royal assent.
This means the Queen has formally approved the Brexit bill and has made it law.
Following the announcement that Article 50 is now law, sterling fell against the dollar, and is now down by 0.33 per cent, and also dropped against the euro to €1.1421.
"The Queen has today given Royal Assent to the Article 50 Bill, giving the government the formal power to trigger Article 50 and deliver on the will of the British people," said Brexit secretary David Davis.
"By the end of the month we will invoke Article 50, allowing us to start our negotiations to build a positive new partnership with our friends and neighbours in the European Union, as well as taking a step out into the world as a truly global Britain."
The Prime Minister told the House of Commons a few days ago that granting the royal assent would be "a defining moment for our whole country as we begin to forge a new relationship with Europe and a new role for ourselves in the world".
MPs voted 494 to 122 in favour of approving the Article 50 bill at the beginning of February, and the legislation was passed in the House of Lords earlier this week. Following the Lords decision, Davis said the UK is on the threshold of “the most important negotiation for our country in a generation.”
Yesterday, Davis said the government does not know the economic impact on the UK of a "no deal" Brexit.
This next step in the Brexit process comes against a backdrop of heightened political turmoil within the UK, as Scotland's first minister pushes for a second independence referendum.
Nicola Sturgeon said earlier this week that she will seek approval from MSPs for a vote to be held between the autumn of 2018 and the spring of 2019.