The team are the second English club to achieve the feat
Manchester United's Europa League win on Wednesday night was the first in the club's illustrious and trophy-laden history.
The 2-0 win over Ajax in Stockholm also helped United join an elite club in European football. They are only the fifth side to win the three main European club trophies along with the UEFA Super Cup.
Along with Juventus, Ajax, Bayern Munich and Chelsea, United have now won the Champions League/European Cup, the defunct Cup Winner's Cup and the UEFA Cup/Europa League.
Juventus were the first team to record the unusual treble. The Italian side won all three trophies in the space of nine seasons in the 1970s and 80s.
Although the other four teams had won a European trophy before Juventus claimed the 1977 UEFA Cup, it took until 1992 for Ajax to become the second team to complete the treble when the won the UEFA Cup.
In 1996, Bayern Munich joined the club, but it took another 17 years for Chelsea to claim the treble. In what can only be described as efficient, Chelsea's added to their Cup Winner's Cup in the space of 12 months, winning the Champions League in 2012 and the Europa League the following season.
On Wednesday night, United became the fifth team to complete the treble. It took them almost 50 years to complete, the longest of any of the three teams.
All five team have also won the UEFA Super Cup. That trophy was introduced in 1972.