The 2002–03 season was Fussball Club Basel 1893's 110th season in their existence and was the club's 9th consecutive season in the Nationalliga A, the top flight of Swiss football. As reigning double holders, the club's main aims for the 2002–03 season were to retain the Swiss Nationalliga A and cup titles. The third aim was to stay in the Champions League as long as possible and, if possible, to reach the group stage. Basel ended the domestic league season as runners-up and Swiss Cup winners. They also reached the second group stage of the Champions League.
The season started well for Basel and they were undefeated in their first seven matches, winning five and drawing two. The following two games were both lost and Basel slipped down in the league table, but they regrouped to win nine and draw two of the following eleven games. A 1–2 home defeat against Grasshoppers cost them the lead in the league table and Grasshoppers ended the league qualifying stage as table leaders at the winter break. In the championship playoff round Basel lost just two away games, but because both ties against Grasshoppers were drawn the Zurich-based club managed to snatch the title by a single point.
Domestic cup
In the round of 32 of the Swiss Cup, Basel won away at lower league team Yverdon-Sport. In the round of 16 and in the quarter-finals Basel eliminated Servette and Young Boys respectively. Lower league club Schaffhausen was defeated 3–0. The final against Neuchâtel Xamax was a one-sided affair: Basel won 6–0 and won the domestic cup.
Champions League
In the second qualifying round of the Champions League, Basel defeated Slovakian club Žilina 4–1. In the third qualifying round they faced Scottish giants Celtic. In the first leg, away at Celtic Park, the home side won 3–1. Basel were able to rescue the tie in the second leg at St. Jakob-Park, coming away with a 2–0 victory, to draw 3–3 on aggregate, Basel proceeding to the group stage on the away goals rule. Basel's success saw them become only the second Swiss team ever to play in the modern Champions League. In the group stage Basel were drawn into Group B along with Valencia, Liverpool and Spartak Moscow. Following a 2–0 home win against Spartak, Basel travelled to Anfield to claim a 1–1 draw against Liverpool. After two good results Basel were brought back down to earth by a 6–2 demolition at Valencia's Estadio Mestalla. However, they bounced back and held Valencia to a 2–2 draw in the next fixture. Basel were now sitting in second place in the group, but needing to win at least one of their last two games and needing Liverpool to fail to pick up more than two points. In matchday five, Liverpool lost 1–0 to Valencia and Basel won 2–0 against Spartak at the Luzhniki Stadium. Basel's place in the last 16 was all but secured, although they still had to make sure they did not lose to Liverpool in the last game of the first group stage. On the last matchday, Basel led 3–0 at half-time through goals from Julio Hernán Rossi, Christian Giménez and Timothée Atouba. Although Liverpool fought back to equalise the game at 3–3 in the second half, Basel qualified for the next round. In the last 16, Basel faced Manchester United, Juventus and Deportivo de La Coruña. They had a poor start, losing back-to-back games at home to Manchester United and away at Juventus. Basel managed to give themselves hope of reaching the quarter-finals by winning 1-0 home and away at Deportivo. Arguably two of Basel's greatest ever European games came next as they held Manchester United to a 1–1 draw at Old Trafford and claimed a 2–1 victory over Juventus at St. Jakob-Park. Despite being knock-out on tie-breaking criteria, Basel had achieved their seasons European aim.
The Qualification round to the 2002–03 league season was contested by twelve teams. The eight teams at the top of the table at the end of the regular season were then to compete in the championship play-off round.
