Barack Obama has spent his first evening in his ancestral home of Kenya.
Air Force One touched down at Nairobi's international airport shortly before 20:10 local time (17:10 GMT) where Mr Obama received a warm welcome from President Kenyatta.
The first serving US president to visit Kenya, the historic trip is also something of a homecoming for Mr. Obama, since Kenya is the birthplace of his father Barack Snr.
The President was greeted by members of his family including his half-sister Auma. The siblings travelled together in the presidential limousine to the hotel where the US leader is staying.
At dinner, the president was joined by more relatives, including the woman known as "Granny" or "Mama Sarah", who helped raise his late father.
During the high profile two-day trip, Mr Obama will address an entrepreneurship summit and he will hold talks with Kenyan President Uhuru Kenyatta.
The trip to Kenya and then Ethiopia is aimed at demonstrating US commitment to fighting terrorism in East Africa.
The President will also discuss trade links and democracy as he pledges to deliver a "blunt message" to African leaders about gay rights and discrimination, despite the fact that Kenya's President has said it is a "non-issue" that won't be on the agenda for the visit.
The capital is in lockdown amidst a massive security operation in anticipation of the President's arrival which comes two years after the al-Shabaab attacks on the West Gate mall which left 67 people dead and the siege of the Garissa University, just three months ago in which Islamist militants murdered 148 people.
The airport's domestic terminal was shut down for the arrival of the President and was patrolled by US marines, CIA and secret service agents and Kenyan soldiers.
Obama will be chauffeured in his bombproof limousine, nicknamed "the Beast". The $1.5m (£970,000) car has 20cm-thick steel plates, 13cm-thick bulletproof glass, Kevlar-reinforced tyres and a presidential blood bank in the boot.
Around 10,000 police officers – roughly a quarter of the national force – were being deployed in the capital and several major roads would be closed to all but emergency and security vehicles.
In an interview with the BBC the President stressed the importance of the visit saying: "Well, I think it is important first of all that the president of the United States underscores our commitment to partnering with countries around the world, even though we're not intimidated by terrorist organisations. Second, the counterterrorism co-operation between the United States and Kenya - and Uganda and other countries - in East Africa - is very strong.
"And part of the subject of the visit is to continue to strengthen those ties to make them more effective. Third, as I wind down my presidency, I've already had a number of visits to Africa. But this gives me an opportunity to focus on a region that I have not been visiting as president, and I'm also going to have the opportunity to talk to the African Union.
"So I'll be the first US president to not only visit Kenya and Ethiopia, but also to address the continent as a whole, building off the African summit that we did here which was historic and has, I think, deepened the kinds of already strong relationships that we have across the continent."
Security concerns are thought to have played a part in the decision for Mr.Obama not to travel to his father's grave and meet family members in the village of K'Ogelo. His father's half-brother, Said Obama, 49, said: "I would have wished that he visit here but to me the most important fact is he's coming to Kenya. He's wearing several hats: he's a family member and he's the president of the US. I know if he doesn't come to K'Ogelo, his spirit will be there with us."
On Sunday (26 July) he will pay tribute to the victims and survivors of the 1998 US embassy bombing and give a speech.
He also becomes the first US leader to address the African Union when he travels to the Ethiopian capital Addis Ababa.
Mr Obama last visited Kenya while serving as a US senator in 2006. The US President wrote about his Kenyan roots in his best-selling 1995 autobiography Dreams From My Father.