Johann Ernst von Sachsen-Weimar

Johann Ernst von Sachsen-Weimar or Johann Ernst of Saxe-Weimar can refer to:


 * Johann Ernst I, Duke of Saxe-Weimar (1594-1626)
 * Johann Ernst II, Duke of Saxe-Weimar (1627-1683)
 * Johann Ernst III, Duke of Saxe-Weimar (1664-1707)
 * Prince Johann Ernst of Saxe-Weimar (1696-1715), sometimes referred to as Johann Ernst IV of Saxe-Weimar; composer and younger son of Johann Ernst III