The name Alexei is a masculine given name of Russian origin. It is derived from the Greek name Alexios, which in turn comes from the Greek word "alexo" meaning "to defend" or "to protect." The name Alexei has been in use in Russia and other Slavic countries for centuries.

In the 10th century, the name Alexei gained significance after the Byzantine emperor Alexios I Komnenos, who ruled from 1081 to 1118. This helped popularize the name in Eastern Europe and the Orthodox Christian world. It was also the name of several Russian tsars and grand dukes, adding to its prestige and widespread use.

One of the most famous historical figures with the name Alexei was Alexei Mikhailovich, who was the Tsar of Russia from 1645 to 1676. He is credited with creating the first Russian navy and expanding the Russian Empire. Another notable Alexei was Alexei Petrovich, the son of Peter the Great, who was born in 1690 and died in 1718.

In the 19th century, the name Alexei was associated with the Russian author Alexei Konstantinovich Tolstoy, who was born in 1817 and died in 1875. He is best known for his historical novel "Prince Serebrenni" and his satirical works.

Another famous Alexei was Alexei Nikolayevich Kosygin, who served as the Prime Minister of the Soviet Union from 1964 to 1980. He played a crucial role in the Soviet economy and foreign policy during the Cold War era.

In more recent times, the name Alexei has been carried by several notable figures, including the Russian businessman Alexei Anatolievich Navalny, who is a prominent opposition leader and anti-corruption activist. Alexei Yagudin, an Olympic figure skating champion from Russia, was born in 1980 and won the gold medal in the 2002 Winter Olympics.