Vladimir Putin is to be inaugurated as president of Russia in a ceremony in the capital, Moscow.
Putin will return to the presidency after an absence of four years in which he served as prime minister.
The outgoing President, Dmitry Medvedev, was widely seen as an ally of Putin.
He won a third term as president in controversial elections in March.
Putin will take the presidential oath at the Grand Kremlin Palace, in a hall that was once the throne room of the Russian tsars.
If he completes his six-year term, Putin will be the longest serving Russian leader since Joseph Stalin.