Nursultan Nazarbayev, who served as Kazakhstan's president since the inception of the office, resigned on Tuesday, bringing nearly three decades in power to an end.
"I have taken the decision to refuse the mandate of the presidency," he said in a speech broadcast on state television.
Mr Nazarbayev, 78, has served in the office since April 1990, but has led Kazakhstan since 1989 while it was still part of the Soviet Union.
He did not give a reason for why he resigned from office in his televised address, but said it was a "difficult" decision, effective until Wednesday.
“I will be with you to serve until the end of my days,” he said. “I see my future task in ensuring a new generation of leaders.”
In Kazakhstan's most recent election, in 2015, he achieved nearly 98 per cent of the vote, giving a mandate for another five-year term.
But the vote was largely a rubber-stamping process. In 2010, Mr Nazarbayev was unanimously elected the nation's leader for life.
Speculation was triggered last month when he asked the Constitutional Council to rule on what powers he would retain in the event of leaving his position voluntarily.
According to Kazakhstan's constitution, the upper house speaker acts as head of state until a new president is elected.
By this law, Senate Chairman Kassymzhomart Tokayev will succeed Mr Nazarbayev until elections scheduled for 2020.
Kazakhstan is Asia's largest energy producer and a key oil-producing nation.
Mr Nazarbayev was in Abu Dhabi last week for the opening ceremony of the Special Olympics, where he met Sheikh Mohamed bin Zayed, Crown Prince of Abu Dhabi.