| Club: | FC St. Gallen |
| Season: | 2020–21 |
| Chrtitle: | Chairman |
| Chairman: | Matthias Hüppi |
| Mgrtitle: | Head coach |
| Manager: | Peter Zeidler |
| Stadium: | Kybunpark |
| League: | Swiss Super League |
| League Result: | 7th |
| Cup1: | Swiss Cup |
| Cup1 Result: | Runners-up |
| Cup2: | UEFA Europa League |
| Cup2 Result: | Third qualifying round |
| League Topscorer: | Kwadwo Duah (9) |
| Season Topscorer: | Kwadwo Duah (10) |
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| Prevseason: | 2019–20 |
| Nextseason: | 2021–22 |
The 2020–21 season was FC St. Gallen's 142nd season in existence and the club's ninth consecutive season in the top flight of Swiss football. In addition to the domestic league, St. Gallen participated in this season's editions of the Swiss Cup. The season covered the period from August 2020 to 30 June 2021.
See main article: 2020–21 Swiss Super League.
See main article: 2020–21 Swiss Cup.
See main article: 2020–21 UEFA Europa League.