Batticaloa lagoon is a long and narrow lagoon situated in the east coast of Sri Lanka with the total area of approximately 11,500 ha of water.

During the dry season the width of the bar mouth of the lagoon decreases and gradually it get closed with the onset of the north east monsoon which piles up the sand bar by the end of dry season.

The lagoon is surrounded by a densely populated region used for cultivating rice, coconut and other crops.

The lagoon has extensive mangrove swamps and some sea grass beds.

The lagoon attracts a wide variety of water birds.