FC 03 Differdange

It was founded in 2003, by a merge of 2 clubs from the city of Differdange: FA Red Boys Differdange and AS Differdange. When the clubs merged, in time for the 2003–04 season, Red Boys was languishing in the bottom half of the Division of Honour, while AS was in mid-table position in the third tier of Luxembourgish football. The new club took Red Boys league position, and was promoted back into the National Division in the 2005–06 season, when the top division was expanded from twelve clubs to fourteen.

Red Boys Differdange had previously been one of the largest and most successful teams in Luxembourgish football, having won the Luxembourg Cup more times than any other team (15). During the 1920s and 1930s, Red Boys competed with Spora Luxembourg for dominance of Luxembourgish football. Red Boys was the more successful of the two, and won thirteen trophies in as many years between 1923 and 1936. Despite the staunch competition (Spora won 8 trophies in the same period), this record has never been matched.

In the 2011–12 UEFA Europa League Differdange 03 progressed to the 3rd qualifying round of the competition after they eliminated Levadia Tallinn 1–0 on aggregate, one of the club's most famous European victories and one of the most historic victories for a club from Luxembourg has ever had in European Competitions. In the 3rd qualifying round they met Olympiakos Volou and lost 3–0 in both legs, 6–0 on aggregate. However, as Olympiakos Volou was presumably involved in a corruption case, UEFA decided on 11 August 2011 that Differdange would progress to the play-off round and meet Paris Saint-Germain, the furthest a club from Luxembourg has reached in European competitions.

In June 2012, after a poor season in BGL League in which they placed 4th, FCD03 changed coach and Paolo Amodio was exempted. Michel Le Flochmoan was appointed as new coach as he is familiar in BGL League: with the F91 Dudelange and with Jeunesse Esch he won multiple championships in Luxembourg.

On 5 and 12 July 2012, FCD03 won against NSÍ Runavík for the first round of qualifying for Europe League with 3–0 and 0–3, with a total of 6 goals in two games. In the second round, FC Differdange 03 faced Belgian club Gent, but were eliminated with an aggregate of 2–4.

On 18 July 2013, they defeated the Dutch club Utrecht in the first leg of 2nd qualifying round of the UEFA Europa League for 2–1. Omar Er Rafik scored both goals. And on 25 July 2013 the made a 3–3 draw against Utrecht in the return, eliminating the Dutch club, which is significantly larger than Differdange, in the UEFA Europa League.

Differdange 03 made history in the 2023-24 season as they won their seventh title in the Luxembourg National Division. This marked their first-ever top-flight title as "Differdange 03", securing it by winning at Stade Jos Haupert.

In 2024-25, Differdange 03 achieved their domestic double, winning both the BGL Ligue (Luxembourg National Division) and the Luxembourg Cup in the same season - their first since winning the double as Red Boys Differdange in 1979.