"On March 18 around 140 events will be held throughout the country, around 356,000 people plan to take part," the Interior Ministry said in a statement.
Crimea's Black Sea port of Sevastopol was the focal point of the celebrations after 95 percent of the city's residents voted to join Russia last year.
More than 96 percent of the voters in the rest of Crimea also said yes, paving the way for the peninsula to rejoin Russia after being part of Ukraine for 60 years.
More festivities, including concerts, are scheduled for Wednesday evening across Siberia and European Russia, including St. Petersburg and the Chechen Republic's Grozny.
Tens of thousands of people have already started gathering in central Moscow to mark the historic event.
Pop singers and other public figures are due to star at a show next to the Kremlin walls, titled "We are Together!"
