Prince Ivan Sergeyevich Gagarin SJ (Иван Сергеевич Гагарин; born in Moscow, 1 August 1814; died in Paris, 19 July 1882) was a Russian Jesuit, known also as Jean-Xavier after his conversion from Orthodoxy to Roman Catholicism.

He entered the service of the state at an early age, and was first named attaché to his uncle, Prince Gregory Gagarin, at Munich, on whose death, in 1837, he acted as secretary to the legation at Vienna.

Gagarin's literary output was considerable; many of his articles which appeared in current reviews and periodicals were afterwards collected and published in book form.

Gagarin's writings were later an influence upon the philosopher Vladimir Solovyov, through whom they helped lay the intellectual groundwork for Metropolitan bishop Andrey Sheptytsky to organize the first Apostolic Exarchate led by Fr.

The "Polybiblion" (Paris, 1882), another review in which articles appeared from the pen of Gagarin, exhibits (XXXV, 166-188) a long list of his writings.

These include: Gagarin also spent several years in Constantinople, where he founded the Society of St. Dionysius the Areopagite, which aimed at reuniting the Greek and Latin Churches.