Naimisha Forest or Naimiṣāraṇya (Devanagari:नैमिषारण्य) was an ancient forest mentioned in the epic Mahabharata and the Shiva Purana. 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 a story teller belonging to the Suta caste viz. 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.
The story regarding the importance of this forest is that, after the great battle of Mahābhārata, sages and saints led by the great sage Saunaka, who were very much concerned about the beginning of Kali yuga, approached Brahma. Being aware of the extreme effects of the yuga, they urged Brahma to show them a place which can stay untouched by the effects of Kali. Brahma takes out a sacred wheel (Chakra) and rolls it down on the earth and says, where ever that wheel stops, that would be the place. The sages follow the wheel, which stops in the forest of Naimisha. Thus, they make it their abode for further penance.
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.