St. Deroin is a ghost town in Nemaha County, Nebraska, United States, originally located below the river bluffs on the Missouri River. Formally chartered in 1854, the town had a popular ferry crossing over the Missouri River for more than three decades. The river changed course, ending the ferry. After a railroad spur bypassed the town, it drew off more commerce. The community rebuilt its school on the river bluff when it was threatened by flooding; this area was also used for the cemetery. The town was completely abandoned by 1920, as flooding had destroyed much of the townsite. The site is at the northern edge of Indian Cave State Park.