Jonynas (masculine), Jonynienė (feminine married), Jonynaitė (feminine unmarried) is a Lithuanian surname. Notable people with the surname include:
- Antanas Jonynas (1923-1976), Lithuanian poet
- Antanas A. Jonynas (born 1953), Lithuanian poet
- Ignas Jonynas, Lithuanian historian
- Vytautas Kazimieras Jonynas, Lithuanian artist