ONEによるWeb掲載のアクションコメディ漫画及びそのリメイク版である村田雄介の同名漫画を原作とするテレビアニメーション。どんな敵でもワンパンチで倒してしまう最強ヒーローの活躍をユーモラスかつ痛快に描いた話題作であり、マッドハウスがアニメーション制作を手がける。監督は「スペース☆ダンディ」シリーズの夏目真悟、シリーズ構成は「TIGER & BUNNY」のシナリオを手がけた鈴木智尋が担当。
３年間に及ぶ特訓の末、無敵のパワーを手に入れた25歳ハゲ頭の男サイタマは、趣味でヒーロー活動を始める。しかし規格外の強さを得てしまったサイタマは、どんな相手だろうとワンパンチであっけなく倒せるようになってしまい、いつしかヒーローとしての情熱を失くしつつあった。そんなサイタマはある日、サイボーグの青年ジェノスと出会い、それをきっかけに“ヒーロー協会”という組織でプロのヒーローとして活動することになるのだが…。
The seemingly ordinary and unimpressive Saitama has a rather unique hobby: being a hero. In order to pursue his childhood dream, he trained relentlessly for three years—and lost all of his hair in the process. Now, Saitama is incredibly powerful, so much so that no enemy is able to defeat him in battle. In fact, all it takes to defeat evildoers with just one punch has led to an unexpected problem—he is no longer able to enjoy the thrill of battling and has become quite bored.
This all changes with the arrival of Genos, a 19-year-old cyborg, who wishes to be Saitama's disciple after seeing what he is capable of. Genos proposes that the two join the Hero Association in order to become certified heroes that will be recognized for their positive contributions to society, and Saitama, shocked that no one knows who he is, quickly agrees. And thus begins the story of One Punch Man, an action-comedy that follows an eccentric individual who longs to fight strong enemies that can hopefully give him the excitement he once felt and just maybe, he'll become popular in the process.
