Thonotosassa is an unincorporated census-designated place in Hillsborough County, Florida, United States. The population was 6,091 at the 2000 census.
The name Thonotosassa comes from the Seminole-Creek words thlonto and sasse, meaning the place was a source of valuable flint. Following the establishment of Fort Brooke in 1824 in what is now Tampa, a road that ran northwest of Lake Thonotosassa was built between Fort Brooke and Fort King in Ocala. Nevertheless, the presence of a Seminole village largely discouraged whites from moving into the area. After the Second Seminole War ended in 1842, whites began to settle.
In 1893, the Tampa and Thonotosassa Railroad opened a 13-mile route between the two growing communities. This line today no longer extends into Thonotosassa, its northern tracks having been removed along with the town depot by the 1980s; but its southern portion remains a busy industrial spur, joining with the CSX main line at Neve Wye.