John Kerry begins Mid East tour with stop in Egypt
Mr Kerry, the most senior American official to visit Egypt since the ousting of President Mohammed Morsi in July, will stay only a few hours.
The visit comes at a time of tension between Washington and Cairo. Mr Morsi is due to go on trial on Monday.
Mr Kerry will go on to tour countries in the Middle East and North Africa.
John Kerry's visit to Cairo was kept under wraps by US officials until he landed - although Egyptian state media did announce his arrival - the first time a US secretary of State has travelled to Egypt on what is known as an unannounced visit for security reasons.
The BBC's Kim Ghattas, travelling with Mr Kerry, says it is the kind of precaution that characterises trips by US officials to countries like Afghanistan and Iraq.
This is a sign of US concerns about continued instability in the country, but it is also a reaction to the high level of anti-American resentment in Egypt, our correspondent says.
Although Washington has not declared the military takeover that deposed the Islamist Mr Morsi a coup, it has de facto suspended military aid to Egypt in compliance with US law.
This has angered supporters of the army, while supporters of the Muslim Brotherhood also feel bitter and accuse the US of letting them down.
Mr Kerry's visit comes a day before the trial of Mr Morsi who is accused of inciting the killing of protesters outside the presidential palace in December 2012.
But the State Department said the timing of Mr Kerry's visit was not connected to the trial, our correspondent adds.
Mr Kerry was meeting the interim leaders that assumed control following July's ouster - President Adly Mahmud Mansour, Prime Minister Hazem el-Beblawi, Foreign Minister Nabil Fahmy and army chief Gen Abdel Fattah al-Sisi.
He is also reported to be meeting, behind closed doors, members of Egyptian civil society alarmed by a crackdown in which hundreds of people have died.
Trade and defence
Saudi Arabia, Israel, Jordan and Morocco are among the countries on the next stages of Mr Kerry's itinerary, which spans 3 to 12 November.
After his Egyptian visit, Secretary Kerry will go on to the Saudi capital, Riyadh.
The Saudi government has recently expressed its disappointment with what it sees as America's hesitant approach in Syria and a lack of support for the new Egyptian government.
Mr Kerry is expected to discuss defence and trade issues with officials, with Syria likely to be high on the agenda across the region.
The secretary of state will also meet Israeli and Palestinian leaders to discuss the peace process in Jerusalem and Bethlehem.
He will then travel to Algeria and Morocco towards the end of the nine-day trip to chair strategic dialogue meetings.
Mr Kerry may also have to face difficult questions over allegations of widespread US spying.
In the wake of revelations sparked by leaks from ex-US intelligence contractor Edward Snowden, Mr Kerry said last week that spying by the US National Security Agency may have gone too far.