- Classification: Kaijū
- Homeland: Monster Island
- Height: Up to 60 m
- Weight: 50,000 t
- Choujin Kyoudo: 20,000 Power(?)
- First Appearance: Manga Chapter 12, Anime Episode 14
Nachiguron (ナチグロン) is a weak Kaijuu that is afraid of humans. Kinnikuman is dispatched to fight him, but realizes Nachiguron is harmless and lets him go. Originally 60 m tall, he shrinks down to around 1 m and moves in with Kinnikuman and Meat in Beverly Park. Meat initially objects to the idea, already having to take care of one big baby (Kinnikuman), but agrees if Nachiguron will take care of himself. He gives Nachiguron a special whistle to blow if he ever gets in trouble and sends him out to get the groceries. Nachiguron is then confronted by the Kaijuu Yakuza for siding with Kinnikuman. He almost blows the whistle, but instead decides to take care of himself. He shows up again from time to time cheering on Kinnikuman or serving as referee, but is not seen again after the Choujin Olympics. In the anime however, he first appears during the Choujin Olympics as Zangyaku-seijin's cowardly minion, but eventually sides with Kinnikuman. He then takes on the role of Kinnikuman's second sidekick and is frequently seen with Meat throughout the rest of the anime.
Nachiguron is bald when he first appears, but in the next chapter he has shaggy blonde hair which is his hairstyle for the remainder of the series. In addition to his cowardice, he is also a very loud snorer. He is named after a kind of candy called Nachiguro (那智黒).
He didn't appear in the Kinnikuman Nisei anime.
- Loser Kaijū (ダメ怪獣, Dame Kaijuu)
- Drop-out Kaijū (落ちこぼれ怪獣, Ochikobore Kaijuu)