Sandwich Harbour (Portuguese: Porto d'Ilhéu), also known as Sandwich Bay, Sandvishawe, Sandvisbaai and Sandfisch Bai is an area on the Atlantic coast of Namibia that includes a bay in the north and a lagoon at the southern end.

There is a shallow lagoon lying south of the bay, separated from it by an area of beach ridges and swales with saltpans.

The area was surveyed in the 1880s by the Royal Navy, but it was considered very inferior to Walvis Bay and no development took place.

In the 1930s, an ambitious project was started to build a guano island in the lagoon using sand pumps imported from the Netherlands.

To enter, visitors need a permit, which can be obtained from the office of the Ministry of Environment and Tourism in Swakopmund.