Cley next the Sea is a large village on the River Glaven in Norfolk, England, 4 miles north-west of Holt and east of Blakeney. It lies within the Norfolk Coast AONB (Area of Outstanding Natural Beauty) and the North Norfolk Heritage Coast and is a Site of Special Scientific Interest.

Despite the name, Cley (pronounced "Cly") has not been "next the sea" since the 17th century, due to land reclamation. There are remnants of the quay, especially the 18th century windmill, now used as a private dwelling.

It is hard to imagine Cley as one of the busiest ports in England, where grain, malt, fish, spices, coal, cloth, barley and oats were exported or imported. The many Flemish gables in the town are a reminder of trade with the Low countries.

The failed land reclamation scheme led to the silting up of the port, and Cley had to find another industry. In the late 19th century they became a holiday resort.

The marshes around Cley are bird reserves in the care of the Norfolk Wildlife Trust.

There is a shell museum 2 miles south of Cley.

Cley is one of the best sites for seeing rare birds in Britain because of its location and habitats. It is a Mecca for "twitchers", the British word for hardcore rare bird chasers.

Cley is the home of the Bird Information Service, publishers of Birding World.