Most of the characters in My Hero Academia are students, which means that they are in their mid-teens (but this depends on the class they are in). However, there are also a number of adult heroes, villains, family members, and so on that make up a significant — if not the major — bulk of the storyline.
Talking about characters' ages in this show is not exactly meaningful, because the answer doesn't make much of a difference to the narrative. On the other hand, it's interesting to compare a person's skills and abilities with how old they are, because such a relationship can reveal quite a lot about said character.
10 All Might (49) Is Much Older Than He Appears
All Might, the strongest hero to grace the world in the current timeline, is almost 50 years old. This fact is in direct conflict with his appearance, whether it's his majestic All Might form or his anemic Toshinori Yagi body.
It's vaguely possible that the One For All has an effect on the aging process, given that none of the previous wielders look very old. On the other hand, this could also be because most of them are killed by All For One before they get the chance to grow old in the first place.
9 Shigaraki Tomura (20) Experiences So Much At Such A Young Age
The revelation that Shigaraki Tomura was Nana Shimura's grandson was nothing short of shocking — least of all because he represents the exact opposite side of morality backed by his grandmother.
Nana's role as a One For All wielder makes the whole thing even more unbelievable, but at least it explains why All For One chooses Shigaraki to inherit his own Quirk. It's sad that Tomura has to experience such a painful dichotomy, that too at the young age of 20.
8 Hawks (23) Is One Of The Youngest Pro-Heroes In The Top Ten
The twenty-three-year-old Hawks, or Keigo Takami, is currently the No. 2 Pro-Hero, having increased by one rank when All Might retires. Still, the fact that he spends his late teens and early twenties in the top ten list is already quite a huge point in his favor.
Keigo doesn't exactly have a blissful childhood, which means that he has somehow managed to separate himself from his suffering and rise to the top. What's more impressive, however, is that Hawks' Hero Agency is founded when he's 18 years old.
7 Izuku Midoriya (16) Is Shaping Up To Be One Of The Greatest Heroes Of His Generation
Izuku enters the story at 14, along with the rest of his compatriots in Classes 1-A and 1-B, all of whom are around 16 years old at this point in the timeline.
He doesn't exactly look his age, either, much like his idol, All Might, but Izuku's childlike appearance only serves to undercut the first impressions people have about him. Besides, what Izuku has accomplished before hitting the voting age is something to be admired, indeed.
6 Best Jeanist (36) Handling Of Fiber Master Is Incomparable
Tsunagu Hakamada, who goes by the Hero name Best Jeanist, is 35 years old when he is "killed" by All For One — and one year older when he returns to the scene of battle with more style than ever.
Sure, he's a bit older than other Pro-Heroes, such as Midnight, Present Mic, Eraser Head, and so on, but Tsunagu compensates for it by displaying a skill level very few people are capable of. In fact, All For One rejects Best Jeanist's Quirk because he knows how much effort is required to manipulate Fiber Master efficiently.
5 Eraser Head (31) Has Learned To Employ Erasure To Near Perfection
Shota Aizawa is one of the more beloved characters in My Hero Academia, in part due to the sheer number of times he has almost sacrificed his life to protect his students.
Eraser Head may not be as powerful as the younger Hawks or the older Best Jeanist, but his talents have nonetheless proven to be crucial in multiple instances. Aizawa's Erasure is overwhelming when applied properly; while the Quirk has quite a few drawbacks, Eraser Head has learned how to employ it to near perfection.
4 All For One (100+) Possesses The Life Force Quirk
All For One is one of the oldest — if not the oldest — characters in the My Hero Academia universe. His titular Quirk allows him to steal everyone else's Quirks, so he naturally uses it to become a villain.
The reason that All For One is so ancient is because of his affiliation with Kyudai Garaki, who "gifts" the former his own Quirk, Life Force (after duplicating it first, of course). The extent to which Life Force can be used is currently unknown, but given Garaki's old-man features, it's not unlimited.
3 Mirio Togata (18) Is In His Final Year At UA Academy
The 18-year-old Mirio Togata is generally considered to be among the strongest students at UA, and he's probably capable of matching several Pro-Heroes in terms of fighting skill.
Mirio's handle on his Permeation Quirk requires the paradoxical combination of intense focus and subtle delicacy, but he does a spiffing job with it anyway. Mirio is about to graduate from UA, but nobody is really sure as to what his plans are after this. Does Japan even have Pro-Hero universities?
2 Endeavor (46) Was The #2 Hero For Twenty-Five Years
Although only three years younger than All Might, Endeavor was ranked below him for at least 25 years. Enji Todoroki mentions that "by age 20, I'd already climbed to the #2 position," further adding that he always "wanted to be the strongest!"
Endeavor gets his wish when All Might retires, but he is unable to revel in his top status — Enji believes that the only honorable way to achieve a better Pro-Hero ranking is by proving himself more powerful, something he can never do now that All Might has permanently lost access to One For All.
1 Dabi (24) Was Believed To Have Died At Age 13
Dabi, born Toya Todoroki, is revealed to be Endeavor's firstborn child who was believed to have been "killed" in a fire at age thirteen. Interestingly, he was around the Todoroki household long enough to form a close relationship with the three younger kids, Fuyumi, Natsuo, and Shoto.
Nine years later, aged 24, Dabi has joined the League of Villains, hellbent on nothing more than bringing his father down. Unfortunately, given Dabi's interaction with Shoto during the Paranormal Liberation War Arc, he doesn't seem to care for any of his siblings anymore.