Theobald I of Navarre was a king who ruled from 1234 to 1253. He was born in 1201 and was a member of the House of Champagne. Theobald became king after the death of his father, Theobald IV of Champagne, and he worked to strengthen the kingdom of Navarre during his reign. He is known for his efforts in diplomacy and governance, which helped to stabilize the region. Theobald I also played a role in the political landscape of France and Castile, forming alliances through marriage and treaties. His reign contributed to the development of Navarre as a significant medieval kingdom.