Naimisha Forest or Naimiṣāraṇya was an ancient forest mentioned in the epic Mahabharata and the Puranas. It lay on the banks of the Gomati River (in Uttar Pradesh) . It lay between the Panchala Kingdom and the Kosala Kingdom. The whole narration of Mahabharata took place at Naimisha forests, during a conclave of sages headed by sage Saunaka, who gathered for a sacrifice to the cause of world peace. In this conclave Ugrasrava Sauti narrated the entire Mahabharata, the story of the great kings of Bharata dynasty to Saunaka. The central part of this story was the history of Kauravas and Pandavas and their battle at Kurukshetra known as Kurukshetra War.
In this forest, the famous Shaunaka rishi, who also wrote the shlokas in praise of Lord Shiva, chanted all the verses of the modern day Mahabharata, which was written by sage Ugrasravas Sauti, in one breath.
Earlier mention of Naimiṣāraṇya is found in Rāmāyaṇa. The colophon of yuddha-kanda (sixth) of Rāmāyaṇa mentions that Lav and Kush, the sons of Ram narrated the epic by Valmiki in the Naimiṣāraṇya in His Ashvamedha-yajna.
Geographically mapping to a presently known location, Naimisha forest is said to be in Sitapur district of Uttar Pradesh state in India.