Jaunutis (Polish: Jawnuta, Belarusian: Яўнут; literally young man; baptized: Ioann, "Jawnuta", "John" or "Ivan"; ca. 1300 – after 1366) was the Grand Duke of Lithuania from his father Gediminas' death in 1341 until he was deposed by his elder brothers Algirdas and Kęstutis in 1345.
According to Jan Tęgowski, a Polish historian, he was born probably between 1306 and 1309.
Jaunutis was not mentioned in any written sources prior to Gediminas' death. There are many theories why Gediminas chose Jaunutis, a middle son, as his successor. Some suggested that he was an acceptable compromise between pagan (Algirdas and Kęstutis) and Orthodox (Narimantas, Karijotas, Liubartas) sons of Gediminas. Others claimed that Jaunutis was the eldest son of Gediminas' second wife; thus the tradition that Gediminas was married twice: to a pagan and to an Orthodox duchess. Another claim is that he was living with Gediminas at the time of his death, and so he was naturally a successor to rule Vilnius and Lithuania.
Very little is known about the years when Jaunutis ruled. Those were quite peaceful years, as the Teutonic Knights were led by the ineffective Ludolf König. His brothers were much more active: Algirdas attacked Mozhaysk, Livonian Order, defended Pskov, Kęstutis was helping Liubartas in succession disputes in Galicia–Volhynia. The Bychowiec Chronicle mentions that Jaunutis was supported by Jewna, presumed wife of Gediminas and mother of his children. She died ca. 1344 and soon after Jaunutis lost his throne. If he was indeed protected by his mother, then it would be an interesting example of influence held by queen mother in pagan Lithuania. However, a concrete stimulus might have been a major reise planned by the Teutonic Knights in 1345. Jaunutis was supported by his brother Narimantas, who traveled to Jani Beg, Khan of the Golden Horde, to form an alliance against Algirdas and Kęstutis. Jaunutis was imprisoned in Vilnius, but managed to escape and went to his brother-in-law Simeon of Russia in Moscow. There Jaunutis was baptized as Ioann, but failed to solicit help (possibly because his sister Aigusta, wife of Simeon, died the same year). Both Jaunutis and Narimantas had to reconcile with Algirdas. Jaunutis became the Duke of Zasłaŭje. He is presumed to have died ca. 1366 because he is mentioned for the last time in a treaty with Poland in 1366, and not mentioned in a treaty with Livonia in 1367. He had three sons, Symeon Zaslawski, Grzegorz Słucki and Michal Zaslawski. Michal ruled Zasłaŭje until his death on August 12, 1399 in the Battle of the Vorskla River.
- Tęgowski, Jan (1999). Pierwsze pokolenia Giedyminowiczów. Poznań-Wrocław: Wydawnictwo Historyczne. p. 190. ISBN 8391356310.
- Rowell, S.C. (1994). Lithuania Ascending: A Pagan Empire Within East-Central Europe, 1295-1345. Cambridge Studies in Medieval Life and Thought: Fourth Series. Cambridge University Press. pp. 280–287. ISBN 978-0-521-45011-9.
- Kiaupa, Zigmantas; Jūratė Kiaupienė; Albinas Kunevičius (2000) . The History of Lithuania Before 1795 (English ed.). Vilnius: Lithuanian Institute of History. p. 118. ISBN 9986-810-13-2.
- Simas Sužiedėlis, ed. (1970–1978). "Jaunutis". Encyclopedia Lituanica. II. Boston, Massachusetts: Juozas Kapočius. p. 516. LCC 74-114275.
- Rowell, S. C. (Spring 1994). "Pious Princesses or Daughters of Belial: Pagan Lithuanian Dynastic Diplomacy, 1279–1423". Medieval Prosopography. 15 (1): 40. ISSN 0198-9405.
- Tęgowski, Jan (1999). Pierwsze pokolenia Giedyminowiczów. Poznań-Wrocław: Wydawnictwo Historyczne. pp. 191–192. ISBN 8391356310.