Theresa May has announced she will resign as Prime Minister on June 7.
In a statement outside 10 Downing Street, she told the waiting press that her resignation was in the "best interests of the country", adding: "I have done my best".
She began to cry as she finished her speech, saying that she had "enormous and enduring gratitude" to hold the role of Prime Minister and "serve the country I love".
The process for electing a new leader will begin in "the following week", with Mrs May continuing as Prime Minister until the process to find her successor has finished.
"I have done everything I can to convince MPs to back that deal. Sadly I have not been able to do so," she said.
"I tried three times. I believe it was right to persevere even when the odds against success seemed high."
Theresa May said she would "deepy regret" not delivering Brexit
She continued: "It is, and will always, remain a matter of deep regret to me that I have not been able to deliver Brexit."
Her statement came after a morning of talks with 1922 Committee chair Sir Graham Brady.
Mrs May added: "The referendum was not just a call to leave the EU, but for profound change in our country. A call to make the UK a country that truly works for everyone. I am proud of the progress we have made."
In the wake of her announcement, the hastag #Mexit began trending on Twitter, a blend of 'May' and 'exit'.
Responding to the news on Twitter, Labour leader Jeremy Corbyn wrote: "Theresa May is right to resign. She's now accepted what the country's known for months: she can't govern, and nor can her divided and disintegrating party.
"Whoever becomes the new Tory leader must let the people decide our country’s future, through an immediate General Election."