Kartha or Karthavu is a Hindu Nair title name that means Lord. It was conferred by the king to powerful Nair families who enjoyed Raja or Naduvazhi status.
Kartha, as a Kshatriya community, ruled smaller principalities or worked mainly in the Army, Police or as tax collectors. They were troop leaders. The Kartha surname is still used, although it is less prominent.
The title Kartha, ("doer"), appears to have been used as a titular name by some of the rulers of Madura. During the Madras census of 1901, the title Kartha was returned by Balijas claiming to be descendants of the Nayak kings of Madura and Tanjore. The Tekkumkur and Vadakkumkur Rajas are said to have first conferred the title Kartha on certain influential Nayar families who were related by blood to the Rajas. In social matters the authority of the Kartha was supreme. Only on important points were higher authorities called on to intercede. Karthas belong to the Illam sub-division of the Nayar caste.
The Samanthans of Chuntampattai and Cherupulasseri were known as Kartha or Karthavu. They were related to the Thirumulpads of Manchery and Amarampalam.
Karthas belong to the Illathu Nair caste. Some of these clans were later elevated to Samanthan Nair.