In the letter, Mugabe said that he decided to step down to allow for the smooth transition of power in the country, according to Reuters.
"I Robert Gabriel Mugabe in terms of section 96 of the constitution of Zimbabwe hereby formally tender my resignation… with immediate effect," the letter reads, according to AFP.
The announcement comes as the parliament has made a decision earlier in the day to impeach Mugabe, giving him 24 hours to leave the office.
Mugabe's letter put an end to the impeachment process triggered by the Zimbabwe's rulig party after the president ignored the Monday deadline to resign. The president was also stripped of all posts in the party along with his wife, Grace Mugabe.
Reuters reported that the news of Mugabe's resignation was met with unbridled joy as Mudendahe was reading the president's address.
The political situation in Zimbabwe has been worsening over the last week after Zimbabwe's military placed Mugabe into custody and took control of government buildings as well as the TV center.
The move was made after Mugabe sacked and ousted from the ruling party his first vice president, Emmerson Mnangagwa, who was considered as a likely successor and enjoys the military’s support.