My Hero Academia's All Might is probably the most iconic character in the series, even above the likes of Izuku "Deku" Midoriya and Katsuki Bakugo, which is saying a lot.
The legendary Number One Pro Hero had the strength, determination, and an incredible sense of justice that made him a hero like no one else. This is also why several plot points in the series are connected to him, such as All For One's machinations, Tomura Shigaraki's motivations, and even the jealousy of Endeavor.
However, something that a lot of My Hero Academia fans have wondered for so many years is who the Number One Pro Hero was before Toshinori Yagi became All Might. It's an interesting question because there were heroes before All Might's arrival, and the answer shows the impact that he had on the series' world as a whole.
Disclaimer: This article contains spoilers for the My Hero Academia series.
Explaining who the Number One Pro Hero was before All Might in My Hero Academia
The most straightforward answer to this question is that the My Hero Academia series never addresses who the Number One Pro Hero was before All Might. In fact, there is an argument to be made that author Kohei Horikoshi never even clarified if there was a hero-ranking system back in Toshinori's early days, so that is something that the series never properly explains.
The reason for never explaining this is that the story didn't require it, as it was never centered around the hero-ranking system beyond Endeavor's character arc and his relationship with his family, which is even more connected with All Might than the system itself.
Furthermore, there is also little evidence of heroes being that much of a big deal before Toshinori's arrival, which is shown by the fact that people like Gran Torino and Nana Shimura were never that familiar to the general populace.
This question also serves to highlight how important All Might was for the My Hero Academia universe, establishing a new era of heroes and destroying All For One's evil empire for several decades. Toshinori's use of the One For All Quirk allowed him to reach heights that no one hero before (and arguably after) reached, which is something that the series addresses through his major relevance in several plot points.
The appeal and legacy of All Might
As mentioned earlier, All Might could very well be the most iconic character in the entire My Hero Academia series, and it is because of how he embodies all the greatest traits of heroism in a very human and relatable way. The character is obviously inspired by DC Comics' Superman, and it is easy to see the similarities since they are both heroic, humble, and believe in humanity, which is their main drive.
There is also the character arc he went through across the series, dealing with his declining powers, teaching his successor, and eventually no longer being a hero, which is an element that is not often seen with heroes in fiction.
In most series, especially shonen anime, the mentor figure is often killed during an epic clash and, therefore, is removed from the story. However, All Might has to face his own retirement and come to terms with his legacy, both the good and the bad.
Final thoughts
There is no confirmation of who was the Number One Pro Hero before All Might in the My Hero Academia series.
Horikoshi never addresses that topic, and it probably serves to highlight the impact Toshinori had on this world, cementing himself as the series' most iconic hero and the most influential by far.