Carthak, or more correctly the Carthaki Empire, is a country that appears in the fantasy books written by Tamora Pierce. It lies to the south of Tortall, across the Great Inland Sea. Its capital city is Carthak City, and the ruling family during the 440's HE is Iliniat. Carthak is a poweful slaveholding empire made up of several conquered lands in the Southern Lands and all the way up to the Roof of the World, a mountain range along the eastern edge of the Eastern Lands.
Carthak was the main setting of the book Emperor Mage, and is the homeland of key supporting character Zaimid Hetnim in the book Trickster's Queen.