Theobald I (French: Thibaut or Thibauld de Bar) (born c. 1158 – died 13 February 1214) was Count of Bar from 1190 until his death, and a Count of Luxemburg from 1197 until his death.^[1] He was the son of Reginald II of Bar and his wife Agnès de Champagne.^[2] He became count when his brother, Henry, was killed in the siege of Acre.^[3]

After his third marriage, he sought to reclaim his wife's lands of Luxembourg, Durbuy and Laroche with the approval of Philip of Swabia.^[4] Theobold therefore besieged the castle at Namur, whereupon a conference was held in which Philip of Namur and his brother Baldwin renounced the disputed territories of Luxembourg, Durbuy and Laroche.^[4] The Treaty of Dinant signed 6 July 1199 at Saint Medard, later made it official.^[4]

During the Albigensian Crusade, Theobald led an army to reinforce Simon de Montfort at the siege of Toulouse [fr] in June 1211.^[1]

After his death in 1214, his eldest son Henry II, from his second marriage; succeeded him as count. His eldest daughter Agnes, from his first marriage, married Frederick II, Duke of Lorraine. His lands in Luxembourg reverted to Waleran III of Limburg, who married Theobald's widow Ermesinde of Namur.^[5] Theobald was buried at St. Mihiel.

Theobald I was married three times; in 1176 he married Laurette of Loon (de Looz), daughter of Louis I, Count of Loon and Agnes of Metz; They had one daughter. Secondly, he married Ermensinde de Bar-sur-Seine, daughter of Guy of Bar-sur-Seine and Petronille de Chacenay, circa 1189;^[6] They had one son and two daughters. Theobald and Ermensinde divorced circa 1195.^[6] He then, married Ermensinde of Luxembourg, daughter of Henry Coecus "the Blind" of Luxembourg and Agnes of Gueldres, in 1197; They had two sons and three daughters.

Children from his marriage to Laurette of Loon (de Looz):

• Agnes (Tomasia), lady of Amance, Longwy and Stenay (b. c 1177, d. 19 Jun 1226); married Frederick II, Duke of Lorraine

Children from his marriage to Ermesinde (Isabella) of Bar-sur-Seine:

• Agnes (d. 1225); married Hugh, lord of Chatillon^[7]
• Henry II, Count of Bar (b. 1190, d. 13 Nov 1239);^[6] married Philippa of Dreux
• Margaret (b. c 1192, d. after 1259); married Heinrich von Salm, lord of Viviers

Children from his marriage to Ermesinde of Luxembourg:^[8]

• Margaret (d. Jul 1270); married firstly Hugh III, count of Vaudémont, secondly Henri de Dampierre, lord of Bois
• Elisabeth (d. between 11 Apr 1262 - 1 Aug 1262); married Waleran of Limburg, lord of Fauquemont and Montjoie
• Henry, lord of Briey, Arrancy, and Marville (d. 1214)
• Renaud (d. Feb 1214)
• unknown daughter (d. before Feb 1214)

• Ambroise (2003). The History of the Holy War: Ambroise's Estoire de la Guerre Sainte. Vol. 1. Translated by Ailes, Marianne. The Boydell Press.
• Evergates, Theodore (1999). "Aristocratic Women in the County of Champagne". In Evergates, Theodore (ed.). Aristocratic Women in Medieval France. University of Pennsylvania Press.
• Evergates, Theodore (2007). The Aristocracy in the County of Champagne, 1100-1300. University of Pennsylvania Press.
• Fassler, Margot Elsbeth (2010). The Virgin of Chartres: Making History Through Liturgy and the Arts. Yale University Press.
• Gade, John A. (1951). Luxemburg in the Middle Ages. Brill.
• Pegg, Mark Gregory (2008). A Most Holy War : The Albigensian Crusade and the Battle for Christendom. Oxford University Press.
• Péporté, P. (2011). Historiography, Collective Memory and Nation-Building in Luxembourg. Brill.