Theobald II (c. 1238 – December 4, 1270) (French: Thibaud or Thibault, Spanish: Teobaldo), called the Young, was Count of Champagne and Brie (as Theobald V) and King of Navarre from 1253 until his death.

He was the eldest son of Theobald I and his third wife, Margaret of Bourbon, Queen of Navarre. He succeeded to his father's titles on his father's death when he was only fourteen years of age. His mother acted as regent with James I of Aragon until 1256, when Theobald came of age. On 27 November, he affirmed the Fueros of Navarre, which limited his power by putting him under the counsel of a tutor from among the aristocracy. He could not make judgements without a council of twelve (a jury) of noblemen. Theobald was not content, however, to be so restricted in royal prerogative before his twenty-first birthday. He received the rites of unction and coronation from Pope Alexander IV in 1257 and 1259 respectively and tried to justify his divine right to rule, a concept foreign until that point in traditional Navarrese politics (though see the reign of Sancho III).

In order to counter the tendency to decentralisation and feudalisation of the noblesse, the king turned to the bourgeoisie. He exacted extraordinary taxes and imposts from them, but they supported him nevertheless because he granted them rights, prestige, and political clout. He extended the fueros of Pamplona to Lanz and Estella to Tiebas and Torralba Del Río. He founded Espinal in 1269.

In other affairs, Theobald continued the policies of his father. He improved the royal administration, of incomes and expenditures, and administered the first census. The count of 1266 indicated the presence of 150,000 inhabitants. Approximately 6.75% of royal revenues were spent on a bureaucracy, 33.84% on the military, and 59.6% to the maintenance of the monarch and his household and duties.

Theobald found support in Louis IX of France, who supported his fellow kings against their vassals with consistency. Theobald married Isabella Louis's daughter, on 6 April 1255. Theobald acted as an advisor of Louis and Louis as an arbiter in Navarre's internal problems. When the daughter, Berengaria, of Alfonso X of Castile was betrothed to Louis, eldest son and heir of King Louis, Castile ceded the use of the ports of Fuenterrabía and San Sebastián to Navarre on 1 January 1256.

In July 1270, Theobald embarked with his father-in-law on the Eighth Crusade to Tunis. Louis died of dysentery at the siege. Theobald died childless at Trapani in Sicily while returning that same year. He was succeeded by his younger brother Henry III of Champagne. His wife Isabella returned home to France, were she died a few months later.

See also

• Ciampolo, a soul found by Dante in the Inferno who defrauded Theobald.