九十九里浜
Chōsei District occupies an area of central Chiba Prefecture to the east of the Bōsō Peninsula. The west of the district ranges from the Bōsō Hill Range to the Kujūkuri Plain; the east of the district runs along the broad coast of the Kujūkuri Beach on the Pacific Ocean. The Ichinomiya River () emerges from the Bōsō Hill Range in Chōnan and empties into the Pacific Ocean at Kujukuri Beach in Chōsei.