An underdog is a party in a competition, frequently in electoral politics or sports, who is popularly expected to lose. If the underdog wins, the event is known as an upset.

Victorious underdogs:

• The defending British fleet was victorious over the "invincible" Spanish Armada in June 1588.
• U.S. President Harry Truman in the 1948 presidential election
• In 1980, the United States hockey team consisting of amateurs and college players defeated the Olympic hockey superpower, the Soviet Union. The amazing upset was called the "Miracle on Ice"
• The 1985 Villanova University basketball team (8 seed) defeated the Georgetown University basketball team (1 seed) in the Men's NCAA Tournament Final
• Minnesota Senator Paul Wellstone in 1990
• Wisconsin Senator Russ Feingold in 1992
• Tennessee Senator Bill Frist in 1994
• Minnesota Governor Jesse Ventura in 1998
• In 2001, the hugely favored Iowa State University basketball team (2 seed) lost to the Hampton University basketball team (15 seed) in the first round of the NCAA Tournament