Udayana was the son of king Sahasranika of Vatsa kingdom, he was married with Vasavadatta, princess of Ujjain.
Two Sanskrit plays of Bhasa deal with Udayana and Vasavadatta.
Pratijnayaugandharayana – The Pledge of Minister Yaugandharayana
Svapnavasavadattam – The dream of Vasavadatta.
Read about Udayana and Vasavadatta here