MS Estonia, previously Viking Sally (1980–1990), Silja Star (−1991), and Wasa King (−1993), was a cruise ferry built in 1979/80 at the German shipyard Meyer Werft in Papenburg.

The ship sank in 1994 in the Baltic Sea in one of the worst maritime disasters of the 20th century. It is the deadliest shipwreck disaster to have occurred in the Baltic Sea in peacetime, costing 852 lives.