They become the first team to win the quartet of European trophies: Champions League/European Cup, European Cup-Winners' Cup, Uefa Cup/Europa League and Conference League. With the Cup-Winners' Cup discontinued only Ajax, Juventus and Bayern Munich can do the same, and the latter two will certainly hope not to find themselves in Europe's third tier competition.
Abdessamad Ezzalzouli gave Betis an early lead, but second-half goals from Enzo Fernandez, Nicolas Jackson, Jadon Sancho and Moises Caicedo secured Chelsea the trophy.
"Coming into this competition was something we had to win. Next season we go again in the Champions League," Chelsea captain Reece James said post-match.
Everything for Enzo Maresca's team hinged around a five-minute spell midway through the second half.
In that window Cole Palmer turned a match the LaLiga side had enjoyed by far the better of into a Chelsea procession, setting up headers first for Fernandez then for Jackson just as the occasion looked to have overwhelmed this young Blues team.
Until that point and against a wall of noise from the Betis end, Chelsea were outplayed and pegged back by an early goal from winger Ezzalzouli.
Then came Palmer's intervention, and once they led it was a simple matter of adding goals from Sancho and Caicedo, as Betis's energy failed them.
Chelsea had gifted them the lead after nine minutes.
Malo Gusto's careless pass through midfield was cut out, the ball breaking to captain Isco who reversed a sumptuous pass in-field to find Ezzalzouli who peeled away. The winger took a touch to make space with his right foot then with his left drilled in into Filip Jorgensen's bottom corner.
James replaced Gusto at the break and slowly Chelsea began to squeeze Betis in their own half.
Finally 65 minutes into the final they produced their first clear opening, or rather Palmer did it alone.
It was he who spotted the forward dart of Argentina midfielder Fernandez, and his arcing cross from wide on the right that the World Cup-winner nodded down through the grasp of Adrian and in.
Then Palmer's chipped ball to the near post found Jackson who adjusted his body well and guided home with his shoulder.
What was left of Betis' spirit drained away when Sancho lifted a wonderful curling finish into the top corner with seven minutes left, before Caicedo drilled home a late fourth.
"It's a great feeling. We knew the game was going to be tough, they made it tough for us in the first half. They got an early goal and it unsettled us. As the game went on, we grew into it," James said.
17°C