The Koliya were a clan of [Nepal] during the time of [Gautama Buddha]. The Koliya, were of the Adicca clan of the Solar Dynasty during the time of Gautama Buddha.
The royal clan to which the mother of Shakyamuni, Mahamaya belonged. The kings of the Koliya and Shakya were brothers, and the families were inter-married. Yashodhara, the wife of Shakyamuni, was also a princess of Koliya royal house. They have claimed status themselves. Other than the Sakyans, they had no status equals in their region, and therefore, members of these two royal families married only among themselves. Both clans were very proud of the purity of their royal blood and had practiced this tradition of inter-marriage since ancient times. For example, Suddhodana's paternal aunt was married to the Koliyan ruler Anjana.
Their daughters, Mahamaya and Mahaprajapati Gautami, were married to Suddhodana, the chief of the Sakyans. Similarly, Yashodhara, daughter of Suppabuddha, who was Anjana’s son, was married to the Sakyan prince, Siddhartha Gautama. Thus, the two royal families were related by marriage bonds between maternal and paternal cousins since ancient times. In spite of such close blood ties, there were occasional rifts between the two royal families, which sometimes turned into open hostility.
The Sakyan and Koliyan ruled on opposite banks of the Rohni river (Rupendehi District of Lumbini, Nepal) Their members were called rajas and their chief was the maharaja. They had autonomy over all domestic administrative matters. However, they were not fully independent states like Vaishali (ancient city) Vesali because both were vassal states of the neighbouring kingdom of Kosala.
The Koliya owned two chief settlements, at Ramagama and at Devadaha.