Theodoric I, born in 965 and died between 1026 and 1027 was the count of Bar and duke of Upper Lorraine from 978 until his death. He succeeded his father, Frederick I and Beatrice, who was daughter of Hugh the Great, count of Paris, and sister to French king Hugh Capet.
His mother was a regent until 987 where in 985, he joined the other Lorrainer lords, including his cousin Godfrey the Prisoner, who they tried repelling the king Lothair of France's invasion: until they hit Verdun where they were captured.
Like most dukes of Lorraine until the Gallicisation of the region in the thirteenth century, Theodoric was loyal to the Holy Roman Emperors where in 1011, deciding to aid Henry II in his war with Luxembourg; he was captured a second time in 1018 in combat with Burgundy, and overcame Odo II of Blois, also count of Meaux, Chartres, and Troyes (later being Champagne). This is when in 1019, associating his son, Frederick, in the government with him is when he briefly opposed the Emperor Conrad II, Henry's successor, but soon joined his supporters.