Theresa May said on Friday that she will step down as leader of the Conservative party, and therefore prime minister, on June 7.
The announcement came after she met with Sir Graham Brady, chairman of the influential 1922 Committee of Conservative backbench MPs.
"Ever since I stepped through the door of Downing Street, I have strived to make Britain a better place," she told reporters outside Downing Street.
"The Brexit referendum was a call for profound change in our country," she stressed. "I did my best to implement the will of the people."
Fighting back tears, she said she was "the second female prime minister, but not the last," and that it had been "the honor of my life to serve the country I love."
She will remain in charge on a caretaker basis until a successor is found.
May has faced incresing pressure to resign in recent months following three unsuccessful attempts to push her Brexit deal through parliament.
A last-ditch ten-point-plan revealed this week was immediately met with derision from friends and foes alike. Opposition leader Jeremy Corbyn called it a "rehash of her old bad deal" and Tory cabinet member.
Leader of the House of Commons Andrea Leadsom left her position on Wednesday as she no longer believed in the government's approach to exiting the European Union.
May had initially planned to publish her Withdrawal Agreement on Friday, but said that would be postponed until June 3. She had described her plan as "one last chance" for Brexit to happen.