Medang Kamulan was a semi-mythological kingdom that believed to be once established somewhere in Central Java according to Javanese mythology. It is either perceived as the predecessor or the actual historical kingdom of Medang Kingdom. "Kamulan" derived from the word "mula" in Javanese means "origin", so "Medang Kamulan" can be interpreted as "pre-Medang" or "Medang the origin".
The kingdom is considered by historians and archaeology scholars as semi-mythological, since there is no actual archaeological remnant and historical sources (such as inscriptions) that mentioned about "Medang Kamulan" kingdom. The name of the kingdom appears in numbers of Javanese myths, legends, and folklores; such as legend of Aji Saka, Dewi Sri, Loro Jonggrang, and in Javanese wayang story it was mentioned that Medang Kamulan was the kingdom where Batara Guru rules and create gamelan. In the legend of Aji Saka, Medang Kamulan was ruled by the evil giant king named Prabu Dewata Cengkar. The Loro Jonggrang legend mentioned that the kingdom was ruled by a king named Prabu Gilingwesi.
The Sundanese tradition recognize this kingdom in their legend as the predecessor of Galuh Kingdom.
Aji Saka legend also mentioned that the Bledug Kuwu mud volcano in Grobogan Regency was the place where the giant serpent Jaka Linglung appear before defeating Prabu Dewata Cengkar.
Line 782 and 783 of second manuscript of 15th century Bujangga Manik mentioned that after leaving Pulutan (correspond to a village name in west Purwodadi, Central Java) he arrived in "Medang Kamulan". Later after crossing the Wuluyu river, he arrived in Gegelang located south of Medang Kamulan. This manuscript was the first written record that mentioned a place named Medang Kamulan, although at that time it was not a kingdom.