Odanad (Malayalam: ōṭānāṭŭ, also known as Onattukara, Onad, Kayamkulam, Kallikoilon and Chirava Svaroopam) was a feudal state in late medieval Kerala. It was established in the 11th century, and disestablished in 1746 when it became part of Travancore after Venad King Marthanda Varma's northern expedition. The last king of Odanad was King Kotha Varma. At the time of its dissolution, it was composed of the present-day taluks of Mavelikkara, Karthikapally, Chenganur in the Alappuzha district and Karunagapally in the Kollam district. In the 15th century, the capital of Odanad was moved from Kandiyoor-Muttom, Mavelikkara to Eruva and Krishnapuram, near Kayamkulam, which led to the state being called Kayamkulam. After this shift, Kayamkulam became the commercial centre of Odanad, while Mavelikkara remained its cultural centre. Odanad was controlled by Nair lords, among whom the ruler of Kayamkulam was the most prominent.
Kayamkulam is better known as Onattukara. Kayamkulam place is spread in karthikapally and mavelikara thaluk. The Sri Krishna Swamy Temple in Eruva, located two kilometres north of Kayamkulam, is one of the prominent establishments in Onattukara.
The word Odanad is a transliteration of the Malayalam word ഓടനാട്, ōṭānāṭŭ, which is a portmanteau of ഓടം, ōṭām meaning boat, and നാട്, nāṭŭ, meaning land, so Odanad means the land of boats. An alternative hypothesis is that the first part of the word derives from ഓടമുള, ōṭāmuḷa, meaning bamboo, and that Odanad means the land of bamboo. Kerala Varma Valiya Koil Thampuran's Sanskrit work Mayura Sandesam describes Odanad as the land of vines.
Kayamkulam is the capital of Odanad, the central figure in the festival of Onam. The state was hence known as Onattukara (ഓണാട്ടുകര, ōṇāṭṭukara), which translates to the land of Onam.
The state was metonymically referred to as Kayamkulam after the capital was moved to the city of Kayamkulam.
Copper plate inscriptions in Thiruvalla, dated to the 11th century, mention Odanad and Mattom, then its capital.