[1] A total of 32 teams competed in the group stage to decide the 16 places in the knockout phase of the 2020–21 UEFA Champions League.
Krasnodar, Midtjylland, İstanbul Başakşehir and Rennes made their debut appearances in the group stage.
For the draw, the teams were seeded into four pots based on the following principles (Regulations Article 13.06): On 17 July 2014, the UEFA emergency panel ruled that Ukrainian and Russian clubs would not be drawn against each other "until further notice" due to the political unrest between the countries.
The fixtures were decided after the draw, using a computer draw not shown to public, with the following match sequence (Regulations Article 16.02):[6] There were scheduling restrictions: for example, teams from the same city (e.g. Real Madrid & Atlético Madrid and Manchester City & Manchester United) in general were not scheduled to play at home on the same matchday (to avoid them playing at home on the same day or on consecutive days, due to logistics and crowd control), and teams from "winter countries" (e.g. Russia) were not scheduled to play at home on the last matchday (due to cold weather).
If two or more teams were tied on points, the following tiebreaking criteria were applied, in the order given, to determine the rankings (see Article 17 Equality of points – group stage, Regulations of the UEFA Champions League):[6] The matchdays were 20–21 October, 27–28 October, 3–4 November, 24–25 November, 1–2 December, and 8–9 December 2020.