The visit was kept secret until the very end.
As recently as Sunday, John Kirby, a spokesman for the US National Security Council, said there were no plans for Biden to visit Ukraine in connection with his trip to Poland, ahead of the so-called February 24 anniversary.
But suddenly the presidents appeared on Monday morning in Kiev.
New weapon pack
In videos on social media, Joe Biden is seen walking around the Ukrainian capital with a large security contingent and Ukrainian President Volodymyr Zelensky.
- A year ago I warned the world about what would happen, Biden said at the short press conference in Kiev.
Almost at the same time as images began circulating on social media, the White House released a written statement by Biden.
According to the statement, Biden will announce a new arms package to Ukraine later this week after talks with President Volodymyr Zelenskyi on Monday.
Eighth journey
Biden is the first sitting US president to visit Ukraine since President George W. Bush in April 2008, British media reports.
As Vice President, under Barack Obama, Joe Biden regularly visited then Ukrainian President Petro Poroshenko.
- On the flight here, a person in my staff asked how many times I had been to Kiev.
I had to think: This is my eighth trip, says Biden.
The US president says he is there to show his support for Ukraine's independence and territorial integrity.
- It is also about much more than Ukraine.
It's about democracy, Biden added.
Stayed for five hours
Biden arrived in Kiev at 8 a.m. Monday morning and departed at 1 p.m. local time, Reuters reports.
The Kremlin received advance information from the White House hours before Biden's departure for Kiev, according to a statement by national security adviser Jake Sullivan.