The 1955 Nippon Professional Baseball season was the sixth season of operation of Nippon Professional Baseball (NPB). This season featured the worst statistical season by winning percentage in NPB history, a .231 winning percentage set by the Taiyo Whales. This season also saw the most wins in a single season by a single team in NPB history, with the Nankai Hawks winning a record 99 games.
The Yomiuri Giants defeated the Nankai Hawks in the Japan Series, 4 games to 3, marking the Giants' 4th NPB championship, all of which to this point had come against the Hawks.