Archimandrite Nikolai Alekseev (January 21, 1869 – April 23, 1952) was a Russian Greek-Catholic priest.
In 1897 he was tonsured a monk and ordained a deacon in the Trinity-Sergius Hermitage, Saint Petersburg.
Some time later, Alekseev was invited to continue his ministry in Petropavlovsk-Kamchatsky, being ordained an abbot.
In 1925 the synod of bishops of the Russian Orthodox Church Outside of Russia (ROCOR) elevated him to the rank of archimandrite and transferred him to Beijing.
In 1928 he formally converted to Catholicism in Beijing, where the Apostolic Delegate Archbishop Celso Benigno Luigi Costantini performed the ritual of joining him to the Catholic Church.