On 21 May 2001, Maltese club Valletta FC completed a incredibly successful season, winning all six of the competitions they entered that year.
Based in the Maltese capital, Valletta had already amassed an impressive collection of silverware including 17 previous league titles. In the 1996-97 season, they participated in five different competitions--the Premier League, the Rothmans Trophy, the Super 5 Cup, the Lowenbrau Cup, and the Super Cup--and won all of them.
In 2001, Malta added the Centenary Cup to celebrate the 100th anniversary of the Maltese Football Association. Valletta won that trophy in December 2000, beating their rivals, Floriana, after having already won the Lowenbrau Cup in August. The Super 5 Cup followed later that month, then the league title in April, and the Rothmans Trophy on 17 May. Four days later, Valletta won their sixth trophy of the season, beating Sliema Wanderers 2-1 (Sliema had also finished as runners-up in the league, the Lowenbrau Cup, and the Super 5 Cup).
Although an impressive accomplishment, Valletta's season was not the best ever. In 1921-22, Northern Irish side Linfield FC won all seven competitions they entered that season. Forty years later, they came close to another sweep, winning seven of eight competitions.