List of Saitama Seibu Lions seasons

The Saitama Seibu Lions are a professional baseball team in Japan's Pacific League based north of Tokyo in Tokorozawa, Saitama Prefecture. They were established in 1950. Before 1979, they were based in Fukuoka, Fukuoka Prefecture, in Kyushu. The team is owned by a subsidiary of Seibu Railway, which in turn is owned by the Seibu Holdings.^[1]

In 76 seasons, they have won the Japan Series thirteen times (1956, 1957, 1958, 1982, 1983, 1986, 1987, 1988, 1990, 1991, 1992, 2004, 2008) and have finished first place in the Pacific League 23 times, most recently in 2019. In the playoff era of the Pacific League (1973–1982, 2004-present), the Lions have reached the postseason thirteen times, most recently doing so in 2022.

• ^a This is determined by calculating the difference in wins plus the difference in losses divided by two.
• ^b The award was not open to the Pacific League until 1989. The award was not given out in the following years: 1971, 1980, 1984, 2000, 2019, and 2024.
  

^[A] Excluding ties, the Fukuoka SoftBank Hawks had a record of 76–63 (.5467) while the Lions had a record of 78–65 (.5454)
^[B] Due to the COVID-19 pandemic in 2020, NPB saw both of their leagues modify their playoff format. The Pacific League decided to modify the traditional Climax Series format and eliminate the First Stage series to instead play only one modified Final Stage series (between the top-2 teams) while the Central League sent the first-place team directly to the Japan Series, which in this case was Yomiuri.