Theobald I (French: Thibaut, Spanish: Teobaldo, often referred to as Thibaut de Navarre and Thibaut de Champagne), also called the Troubadour and the Posthumous, was Count of Champagne (as Theobald IV) from birth and King of Navarre from 1234. He initiated the Barons' Crusade, was famous as a trouvère, and was the first Frenchman to rule Navarre.
Born in Troyes, he was the son of Theobald III of Champagne and Blanche of Navarre, the youngest daughter of Sancho VI of Navarre. His father died less than a week before he was born, and Blanche ruled the county as regent until Theobald turned twenty-one in 1222.
Theobald succeeded his uncle Sancho VII of Navarre as King of Navarre. Theobald was in Pamplona at the time of Sancho's death and he immediately affirmed the fueros of the realm. This greatly increased his resources (not to mention his prestige), and the remaining years of his rule were far more peaceful and prosperous. The lords and barons of Northern France who had been in conflict with Theobald IV in 1229 left him in peace, realizing that as the new king of Navarre, his position was too strong to challenge.
Theobald died at Pamplona, on a return from one of his many visits to Champagne. He was buried in the Cathedral of Pamplona. He was succeeded first by his elder son Theobald II and then by his younger son Henry I.