was a town located in Atetsu District, Okayama Prefecture, Japan.
As of 2003, the town had an estimated population of 3,152 and a density of 41.32 persons per km ò. The total area was 76.29 km ò.
On March 31, 2005, Tessei, along with the towns of à Âsa, Shingà  and Tetta (all from Atetsu District), was merged into the expanded city of Niimi.
The town is known for its nature reserve, , which was designated as a National Natural Monument.