Nusa Lembongan is one of three small offshore islands which make up a sub-regency of Klungkung, the others being: Nusa Penida and Nusa Ceningan. Nusa Lembongan is the only one of the three islands within the sub-regency to have any tourist infrastructure and is a popular side destination for visitors to Bali.

Nusa Lembongan is approximately 8 square kilometres in size with a permanent population estimated at 5,000. Twelve kilometres of the Badung Strait separates Nusa Lembongan from Bali. Nusa Lembongan is surrounded by coral reefs with white sand beaches and low limestone cliffs. Nusa Lembongan is separated from Nusa Ceningan by a shallow estuarine channel which is difficult to navigate at low tide. There is a suspension bridge linking Nusa Lembongan and Nusa Ceningan and this takes foot and motorbike traffic only. There are no permanent waterways on Nusa Lembongan.

There are three main villages on the island. Jungut Batu and Mushroom Bay are the centres of the tourist-based industry and activities on the island whilst much of the permanent local population resides in Lembongan Village.