Spanish Fort Site is an archaeological earthwork in Mississippi’s Delta along the Sunflower River, one of three major earthwork sites in the southern Yazoo River valley. Despite its name, it was not built by the Spanish and is understood as a ceremonial enclosure rather than a fortification. Investigations found a semicircular earthwork with mounds and artifacts from several cultural periods, making its dating complex. Comparative study suggests the enclosure was probably built in the early Middle Woodland period, during the transition from Tchefuncte to Marksville culture. Part of the site was listed on the National Register of Historic Places in 1988 for the insight it preserves into ceremonial life and long-term occupation in the lower Mississippi Valley.