Htin Kyaw, 71, was sworn in as president in 2016 after the National League for Democracy (NLD) won the November 2015 election.
He was taking a rest following health issues, the government said. Speculation over Htin Kyaw’s ill health has increased in recent months over his rapid and visible loss of weight.
Speaker Win Myint of the NLD would be the 10th president since independence in 1948.
MPs have seven working days to make an appointment under the military-drafted 2008 constitution.
The charter bans State Counsellor Aung San Suu Kyi from holding the presidency because her children are foreign nationals.
The 67-year-old Speaker is believed to be one of Suu Kyi’s favourites among the NLD hierarchy.
Analyst Richard Horsey said the new president had to be from Suu Kyi’s “inner circle of trusted loyalists”.
“The president has full executive authority under the constitution so it requires a personal pact in order for Aung San Suu Kyi to maintain the situation where she is the actual seat of power,” Horsey said.
Win Myint has had a tight grip on the parliament and his critics, including from within the NLD, accuse him of stifling parliamentary debate.
“The discussion about the replacement has been around for a while so this was well expected,” said Liu Yun from the China-based Han Yue Consultancy. “It should have a fairly limited impact on the political equation in Myanmar.”
He said the role of the president “isn’t that influential as Suu Kyi makes the final call, so the impact will be limited”.
The reality, however, is that military chief, Min Aung Hlaing, is far more powerful than the president or Suu Kyi.
Outgoing Htin Kyaw previously served as an executive for the Daw Khin Kyi Foundation, a charity named after Suu Kyi’s late mother.
He was one of the few people allowed to visit her while she was under house arrest, he studied with her in Oxford and was close to her husband.
The economics graduate was elected in 1990 for the NLD in the general election that was cancelled by the military.
“We’ve been hearing that he [Htin Kyaw] might make such a step for some months, so this is no surprise,” said Dr Khin Zaw Win, director of the Tampidipa Institute in Yangon.
“I think the new person will have to take some more responsibility from the state counsellor. It was a mistake for her to centralise so much authority, leaving U Htin Kyaw as a puppet.”
President Htin Kyaw and his Russian counterpart Vladimir Putin in 2016. Picture credit: Wikimedia