Tya Maru () was a Japanese train ferry constructed by Japanese National Railways (JNR) which sank during a typhoon, later known locally as the Tya Maru Typhoon, in the Tsugaru Strait between the Japanese islands of Hokkaid and Honsh on September 26, 1954. JNR announced in September 1955 that 1,153 people aboard were killed in the accident. However, the exact number of fatalities remains unknown because there were victims who managed to obtain passage on the ship at the last minute, and others who cancelled their tickets just before the incident occurred.

A train ferry is a ship (ferry) designed to carry railway vehicles. Typically, one level of the ship is fitted with railway tracks, and the vessel has a door at the front and/or rear to give access to the wharves. In the United States, train ferries are sometimes referred to as "car ferries", as distinguished from "auto ferries" used to transport automobiles. The wharf (sometimes called a "slip") has a ramp, and a linkspan or "apron", balanced by weights, that connects the railway proper to the ship, allowing for tidal or seasonal changes in water level.

While railway vehicles can be and are shipped on the decks or in the holds of ordinary ships, purpose-built train ferries can be quickly loaded and unloaded by roll-on/roll-off, especially as several vehicles can be loaded or unloaded at once. A train ferry that is a barge is called a car float or rail barge.