Dielette, Maritime port in Flamanville and Tréauville, France.

Dielette is the harbour shared by Flamanville and Tréauville, where the coastal river La Diélette, rising at Grosville and running some fifteen kilometres, empties into the Port-Diélette basin. A new marina, inaugurated in 1997, was added beside the old fishing port. At the roadside a grey pole carries a yellow sign marked "D 4" above a white sign with a red border reading "ÉLETTE".

The port was built in the 18th century by the lords of Flamanville; René Bougard's routier records the "new port" completed in 1732, with a jetty sheltering ships from westerly winds. During the wars of the First Empire it served as a refuge. A new Port-Diélette was added to the old fishing harbour in 1997, shared between Flamanville and Tréauville.

The name Diélette comes from the coastal river that rises at Grosville and flows about fifteen kilometres into the harbour basin. The old fishing village kept its small fishing port, and in 1997 a new marina, Port-Diélette, was added alongside it. The signpost at the entrance reads "D 4" and "ÉLETTE".

The signpost at the harbour entrance marks the D4 road with a white sign reading "ÉLETTE". Ferries leave from here for Guernsey (Saint Peter Port), and some routes call at Alderney first. The harbour lies at the mouth of the Diélette, a coastal river about fifteen kilometres long rising at Grosville.

The coastal river La Diélette rises at Grosville and runs about fifteen kilometres before entering the basin of Port-Diélette. Beneath the sea nearby lay the Cabotière iron mine, whose ore was rich in iron but whose galleries flooded; it closed in 1962.