Grand Duke George Mikhailovich Romanov tied the knot with Italian fiance Victoria Romanovna Bettarini at St. Isaac's Cathedral in St. Petersburg in an elaborate religious ceremony with hundreds of foreign guests in attendance.
The Romanov dynasty ruled Russia for 300 years before Nicholas II abdicated in 1917. Nicholas II, his wife, and five children were killed by a revolutionary firing squad the following year.
Royal Family expert Nicolas Polonsky described the event as "truly historical."
"This is the Romanov family's first Italian lady. Never before has an Italian become a Russian princess. We are now witnessing a totally unique event," he said.
George Mikhailovich was born in Spain to Grand Duchess Maria Vladimirovna of Russia - the self-proclaimed heir to Russia's imperial throne - and her husband Grand Duke Mikhail Pavlovich of Russia. He lived in France and Spain for most of his life.
His great-grandfather, Grand Duke Kirill Vladimirovich, managed to escape Bolshevik violence during the 1917 revolution to Finland. He and his family later relocated to Western Europe.
Bettarini, 39, converted to the Russian Orthodox faith last year and took the name Victoria Romanovna.