Data from the country's election administration body (STAE) with all votes counted on Thursday showed Ramos-Horta secured a decisive 62 per cent win in Tuesday's ballot, well ahead of his opponent, incumbent president Francisco "Lu Olo" Guterres with 37 per cent.
"I have received this mandate from our people, from the nation in an overwhelming demonstration of our people's commitment to democracy," Ramos-Horta told reporters in Dili.
The 72-year-old statesman is one of East Timor's best known political figures and was previously president from 2007-12, and prime minister and foreign minister before that.
Addressing concerns over political instability in the country, Ramos-Horta said he would work to heal divisions in East Timor, also known as Timor Leste.
"I will do what I have always done throughout my life... I will always pursue dialogue, patiently, relentlessly, to find common ground to find solutions to the challenges this country faces," he said.
Ramos-Horta said he had not spoken to his election rival Lu Olo, but had received an invitation from the president's office to discuss a handover of power.
Home to 1.3 million people, the half-island and predominantly Roman Catholic nation of East Timor has for years grappled with bouts of political instability and the challenge of diversifying its economy, which is largely dependent on oil and gas.
Ramos-Horta said he expected East Timor to become the 11th member of the regional bloc the Association of Southeast Asian Nations (ASEAN) "within this year or next year at the latest".
East Timor currently holds observer status in ASEAN.
The president-elect, who will be inaugurated on May 20, the twentieth anniversary of the country's restoration of independence, said he would work with the government to respond to global economic pressures, including the impact on supply chains from the war in Ukraine and COVID-19 lockdowns in China.
"Of course, we start feeling it here in Timor Leste. Oil prices went up, rice went up, that is a reality of what has happened in the world. It requires wise leadership."
