Jurij Mihajlovič Kasjan (also spelled Yuriy Mikhailovich Kasyan, Iurii Mihajlovič Kasian, pron. Yooreey Mikhaylovich Kasyan; Юрий Михайлович Касьян; born May 6, 1961 in Snjatin) is a Ukrainian speleologist, most known for his work in cave exploration, especially as the Call of the Abyss research project coordinator. He was heading the speleological expeditions to caves of the Arabika massif in Abkhazia and, with Aleksandr Klimčuk, to Aladaglar massif in Turkey. Some of the world's deepest caves were explored, including the first cave, deeper than 2,000 m, the Krubera-Voronja Cave.