Kotehashi Shell Mound, Archaeological shell mound in Chiba, Japan.

Kotehashi Shell Mound is a horseshoe-shaped shell midden on a plateau about 26 meters above sea level in the Satsukigaoka neighborhood of Chiba. Its shell layer spans 200 meters east-west and 150 meters north-south, opening to the northeast. The site is maintained as a historic park with a playground.

The mound was built during the transition from the late to the final Jōmon period. Full-scale excavations were conducted in 1951, 1956 and 1964 by Meiji University, Tokyo Gakugei University and Chiba University. The Satsukigaoka housing complex was built in 1968, altering the surrounding terrain, but the shell mound was preserved. It was designated a National Historic Site in 1981.

This site reveals how early inhabitants used the sea and which marine creatures they preferred to eat. The layers show how their eating habits changed over time.

The site is now a historical park and playground, about five minutes on foot from the Satsukigaoka Daiichi stop on the Keisei bus from Shin-Kemigawa Station on the JR Sobu Main Line. Satsukigaoka East Elementary School pupils pass through it on their way to and from school.

The stacked shell layers act like tree rings and allow scientists to reconstruct environmental conditions from different time periods. Through this method, researchers can also detect when climate shifted or when new fish species appeared in the region.