Zimbabwe's President Robert Mugabe says he is resigning immediately and voluntarily in order to have a "smooth transfer of power" after 37 years in charge.
The letter was read out in a cheering, dancing Parliament, which had been pursuing impeachment of the 93-year-old Mugabe, the world's oldest head of state.
The resignation comes at the end of a week of extraordinary events that began with the military moving in last week, angered by Mugabe's firing of his longtime deputy and the positioning of the unpopular first lady to succeed him.
Impeachment allegations against Mugabe included that he "allowed his wife to usurp constitutional power" and that he is "of advanced age" and too incapacitated to rule.
Mugabe also was accused of allowing unpopular first lady Grace Mugabe to threaten to kill the recently fired Vice President Emmerson Mnangagwa and other officials.
Zimbabwe's Parliament has erupted in cheers as the speaker announces the resignation of President Robert Mugabe.
The speaker stopped impeachment proceedings to say they had received a letter from Mugabe with the resignation "with immediate effect."
It is an extraordinary end for the world's oldest head of state after 37 years in power.