After a red-carpet welcome for Air Force One, Obama met Myanmar's reformist President Thein Sein and called on the former general to speed up the country's march out of decades of iron-fisted military rule.
"Over the last year and a half, a dramatic transition has begun, as a dictatorship of five decades has loosened its grip," Obama said afterwards in a major address at Yangon University during his whirlwind visit.
"This remarkable journey has just begun, and has much further to go," he said. "The flickers of progress that we have seen must not be extinguished. They must be strengthened."
Over the past few decades, "our two countries became strangers", added Obama, who is on his foreign trip since winning re-election this month.
"But today, I can tell you that we always remained hopeful about the people of this country. About you. You gave us hope. And we bore witness to your courage."
In once unthinkable scenes, Obama's motorcade passed tens of thousands of flag-waving supporters -- some chanting "America" -- lining the streets of Yangon, the backdrop for several bloody crackdowns on pro-democracy uprisings.