The draw for the group stage was held on 31 August 2018, 13:00 CEST, at the Grimaldi Forum in Monaco. The 48 teams were drawn into twelve groups of four, with the restriction that teams from the same association could not be drawn against each other. For the draw, the teams were seeded into four pots based on their 2018 UEFA club coefficients. 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. Moreover, the draw was controlled for teams from the same association in order to split the teams evenly into the two sets of six groups for maximum television coverage. On each matchday, one set of six groups played their matches at 18:55 CET/CEST, while the other set of six groups played their matches at 21:00 CET/CEST, with the two sets of groups alternating between each matchday. The following pairings were announced by UEFA after the group stage teams were confirmed:
The fixtures were decided after the draw, using a computer draw not shown to public, with the following match sequence : Note: Positions for scheduling do not use the seeding pots, e.g., Team 1 is not necessarily the team from Pot 1 in the draw.
There were scheduling restrictions: for example, teams from the same city in general were not scheduled to play at home on the same matchday, and teams from "winter countries" were not scheduled to play at home on the last matchday.
Teams
Below were the participating teams, grouped by their seeding pot. They included:
Group winners and runners-up advance to round of 32
;Notes
Format
In each group, teams played against each other home-and-away in a round-robin format. The group winners and runners-up advanced to the round of 32, where they were joined by the eight third-placed teams of the Champions League group stage.
Tiebreakers
Teams were ranked according to points, and if tied on points, the following tiebreaking criteria were applied, in the order given, to determine the rankings :
Points in head-to-head matches among tied teams;
Goal difference in head-to-head matches among tied teams;
Goals scored in head-to-head matches among tied teams;
Away goals scored in head-to-head matches among tied teams;
If more than two teams are tied, and after applying all head-to-head criteria above, a subset of teams are still tied, all head-to-head criteria above are reapplied exclusively to this subset of teams;
Goal difference in all group matches;
Goals scored in all group matches;
Away goals scored in all group matches;
Wins in all group matches;
Away wins in all group matches;
Disciplinary points ;
UEFA club coefficient.
Groups
The matchdays were 20 September, 4 October, 25 October, 8 November, 29 November, and 13 December 2018. The scheduled kickoff times were 18:55 and 21:00 CET/CEST, except for a few matches whose kickoff times were 16:50 CET/CEST. Times are CET/CEST, as listed by UEFA.
