Ignas Jonynas (January 24, 1884 – July 14, 1954) was a Lithuanian diplomat, historian, and university professor. As a diplomat he is known for negotiations with the Second Polish Republic and League of Nations regarding Vilnius Region. As a historian he specialized in the history of Lithuania in the 13–16th centuries and lectured at the University of Lithuania and Vilnius University from 1924 until his death. He published little, but had a formative influence on subsequent generations of historians.