The Okadaira Shell Midden (陸平貝塚, Okadaira kaizuka) is an archaeological site in the Iide area of the village of Miho, Ibaraki Prefecture, in the northern Kantō region of Japan containing a late Jōmon period shell midden.

The middens associated with such settlements contain bone, botanical material, mollusc shells, sherds, lithics, and other artifacts and ecofacts associated with the now-vanished inhabitants, and these features, provide a useful source into the diets and habits of Jōmon society.

The Okadaira ring-shaped shell midden and its village ruin date from the early to late Jōmon period (about 7000 to 3500 years ago), and is located in the center of the south coast of Lake Kasumigaura at an elevation of 20 to 30 meters, on what is believed to have been an island in Lake Kasumigaura during this period.

The shell layer is distributed in a ring shape, and Jōmon pottery and clay figurines, stone tools, bone fishhooks and shellfish products have been excavated.

Based on the excavation surveys, an archaeological park with restorations of pit dwellings has been created along with an on-site museum.