Simon I (1076 – 13 or 14 January 1139) was the duke of Lorraine from 1115 to his death, the eldest son and successor of Theodoric II and Hedwig of Formbach and a half-brother of Emperor Lothair III. Continuing the policy of friendship with the Holy Roman Emperor, he accompanied the Emperor Henry V to the Diet of Worms of 1122, where the Investiture Controversy was resolved.