Mar Ukva (or Mar Ukba; other: Mar Ukva (I))(also known as Natan Tzutzita) was a Jewish Amora sage of Babylon, of the first generation of the Amora era. He served as an Exilarch during the days of Samuel of Nehardea, who was also his Rabbi, but at the same time, Samuel was subordinated to Mar Ukva in Ukva's capacity as "Av Beit Din" - Chief of the rabbinical Sanhedrin court, and its second-highest-ranking member. He resided at Kafri city, Babylonia, where his "Beth din" - rabbinical court - was also located. According to the Iggeret Rav Sherira Gaon, he was appointed Exilarch after R. Huna Kamma died. In the Talmud it is storied that he was a righteous man and used to give "Tzedakah" ("Charity") anonymously, in order not to shame the needy he handed the charity to. As a disciple of Samuel of Nehardea, he also had knowledge in medicine.