Negombo Lagoon is a large estuarine lagoon in Negombo, south-west Sri Lanka.
The lagoon is fed by a number of small rivers and a canal. It is linked to the sea by a narrow channel to the north, near Negombo city. It is surrounded by a densely populated region containing rice paddies, coconut plantations and grassland. The land is used for fishing and agriculture. The lagoon has extensive mangrove swamps and attracts a wide variety of water birds including cormorants, herons, egrets, gulls, terns and other shorebirds. Negombo, Katunayake, Seeduwa are some nearby towns.