Otto I of Olomouc (1045 - 1087) was Duke of Olomouc in Moravia from 1061 to his death in 1087.
He was the youngest son of Bretislaus I, Duke of Bohemia and Judith of Schweinfurt. After his father's death, his older brother was crowned as Spytihnev II, Duke of Bohemia and Otto was with his brother Conrad duke in Brno, but after struggles with his brother Vratislaus of Olomouc he took refugee in Prague. In 1061 Spytihnev died and Otto's other older brother, Vratislaus II of Bohemia was crowned. After that moment he received the government of Olomouc. Otto married the princes Euphemia of Hungary, daughter of the King Béla I of Hungary before 1073.
Hungary's internal political situation was extremely chaotic in that time. The King Salomon of Hungary conspired several times against his cousins the Hungarian princes Géza and Ladislaus, and tried to kill he first sending assassins to his camp followed by an army. Running for help Ladislaus assisted his brother and in 1074, Otto joined the brothers of his wife in Battle of Mogyoród attacking the forces of the King Salomon. The result of the battle was a complete victory and Géza was crowned as King of Hungary and Salomon exiled.