Matsya (Sanskrit: मत्स्य) was a Vedic kingdom and later became a part of sixteen Mahajanapadas, which also appears in Hindu Epic literature. The capital of Matsya was at Viratanagari (present-day Bairat, in Rajasthan) which is said to have been named after its founder king, Virata.

Matsya was a prominent ancient Indian janapada (i.e., kingdom or state) located in the Madhyadesa (central zone). According to the Manusmriti, its territory was situated within the geographical limits of Brahmarsidesa.

Matsya kingdom was founded by king Matsya who was the twin brother of Satyavati and who was contemporary to Bhishma.