Krishna Janmashtami (Devanagari कृष्ण जन्माष्टमी, IAST: Kṛṣṇa Janmāṣṭamī), also known simply as Janmashtami or Gokulashtami, is an annual Hindu festival that celebrates the birth of Krishna, the eighth avatar of Vishnu. It is observed according to Hindu luni-solar calendar, on the eighth day (Ashtami) of the Krishna Paksha (dark fortnight) in the month of Bhadrapada of the Hindu Calendar, which overlaps with August and September of the Gregorian calendar.

It is an important festival particularly to the Vaishnavism tradition of Hinduism. Dance-drama enactments of the life of Krishna according to the Bhagavata Purana (such as Rasa lila or Krishna Lila), devotional singing through the midnight when Krishna is believed to have been born, fasting (upavasa), a night vigil (jagarana), and a festival (mahotsava) on the following day are a part of the Janmashtami celebrations. It is celebrated particularly in Mathura and Brindavan, along with major Vaishnava and non-sectarian communities found in Manipur, Assam, West Bengal, Odisha, Madhya Pradesh, Rajasthan, Gujarat, Maharashtra, Karnataka, Kerala, Tamil Nadu, Andhra Pradesh and other regions.

Krishna Janmashtami is followed by the festival Nandotsav, which celebrates the occasion when Nanda Baba distributed gifts to the community in honour of the birth.