The group stage of the 1998–99 UEFA Champions League began on 16 September 1998 and ended on 9 December 1998. Eight teams qualified automatically for the group stage, while 16 more qualified via a preliminary round. The 24 teams were divided into six groups of four, and the teams in each group played against each other on a home-and-away basis, meaning that each team played a total of six group matches. For each win, teams were awarded three points, with one point awarded for each draw.
Seeding was based on the UEFA associations 1998 raking,[1] similarly to the previous season.[2] Title holders and champions of nations ranked 1–5 were put in the Pot 1. Champions of nations ranked 6–7 as well as runners-up of nations ranked 1–5 (except France) formed Pot 2. The remaining qualified runners-up (from the nations 6–8) and champions of top three nations ranked below 7 formed Pot 3. Finally, the remaining six national champions formed Pot 4.
Key to colours in group tables
Group winners and best-ranked runners-up advance to the knockout stage
^CET (UTC+1) for matches from 4 November 1998, and CEST (UTC+2) for matches to 21 October 1998.
^Panathinaikos played their home match at Nikos Goumas Stadium instead of their regular stadium Olympic Stadium due to The Rolling Stones concert being held there.[5]
^Originally scheduled for 25 November, delayed for political tensions between Turkey and Italy due to the Öcalan affair.
^Real Madrid were ordered to play one match away from their usual home ground due to crowd trouble at their last home game in UEFA competition against Borussia Dortmund in the first leg of the 1997–98 Champions League semi-final. Fylan, Kevin (6 April 1998). "Football: Real punished for trouble at European Cup tie". The Independent. Independent News and Media. Retrieved 15 February 2010.