Air Force One touched down at Nairobi's international airport, AFP reporters said, marking the start of a weekend visit during which the president will address an entrepreneurship summit and hold talks on trade and investment, security and counter-terrorism, and democracy and human rights.
Obama was greeted by Kenyan President Uhuru Kenyatta with a handshake and embrace as he stepped off Air Force One. A massive security operation was also under way to protect Obama.
Parts of the Kenyan capital Nairobi have been locked down, and airspace closed during the president's arrival late Friday and his departure late Sunday for neighbouring Ethiopia.
Top of the list of security concerns is Somalia's Shebab militants, who have staged a string of suicide attacks, massacres and bombings on Kenyan soil, including the bloody attack on the Westgate shopping mall in the heart of the capital nearly two years ago that left 67 dead.
Excitement has been building in Kenya for weeks, with the visit painted as a major boost for the country's position as an African hub -- something that has taken a battering in recent years due to Shebab attacks and political violence that landed Kenyan leaders in the International Criminal Court.