Bayer Leverkusen won the first Bundesliga title in their history with a 5-0 win over Werder Bremen on Sunday, securing the championship with five games to play.
Alonso's team remain unbeaten in all competitions this season having broken Bayern Munich's German record of 32 games without a defeat in all competitions in February. The run now stands at 43 in all competitions.
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"It feels great. I have the feeling this is not just for us, this is for so many people that have been chasing this dream for so many years," Alonso said after the game. "Past coaches are part of it as well. It is very special when it is the first time for everything, and this is the most difficult title probably."
Leverkusen took the lead in the 25th minute through Victor Boniface's penalty, and a long-range strike from Granit Xhaka in the second half added comfort to the score in front a rapturous BayArena crowd.
Florian Wirtz added the final touches with a superb effort in the 68th minute that left Michael Zetterer with almost no chance in the Werder Bremen goal. Wirtz scored again with a few minutes remaining, causing some fans to run onto the pitch. Wirtz and other players motioned the fans off the grass, and the rest of the game was played under the smoke of pyrotechnics.
There was another disruption as Wirtz completed his hat trick with more fans racing out of the stands, causing the referee to blow the full-time whistle and sparking scenes of sheer jubilation among players, fans and staff alike.
The result means Bayern's run of 11 consecutive Bundesliga titles has come to an end, with the Bavarian giants and Stuttgart both 16 points behind.
It caps a remarkable transformation for Leverkusen since Alonso took over as coach in October 2022. The club was second-bottom at the time after eight rounds of last season, with the former Spain international eventually leading them to a sixth-placed finish.
That momentum carried into this season, with the signings of Boniface, Xhaka, Jonas Hofmann and Alejandro Grimaldo all acclimatising to the Rhineland-based club with ease and playing crucial roles as they won the title.
"All of them, the 25 players of the squad," Alonso said when asked who deserved credit. "You need to push them and they accept that. They knew they are part of something special. We have a proper team. We change players and they deliver. That's one of the successes of this team. Each player felt they were important."
The silverware helps rid Leverkusen of the unwanted 'Neverkusen' tag that has plagued them as Germany's perennial runners-up. They have finished second in the league five times, three more than any other side in the country who hadn't won the title until this season, and last won a trophy in 1993.
In 2002, the club infamously lost both the German Cup and Champions League finals as well as surrendering a five-point Bundesliga lead in the last three rounds of the season to finish the year trophy-less.
This season, however, a 3-0 win over Bayern in February helped alleviate fears of a similar caving and demonstrated that this Leverkusen team was capable of shaking off those historical concerns.
Alonso confirmed in March that he will remain as head coach of the team for next season despite mounting speculation linking him to Bayern, who are parting ways with Thomas Tuchel at the end of the term, and Liverpool, whose manager Jurgen Klopp is leaving after nearly nine years at the helm.