Otheon (オセオン Oseon?) is a fictional country in Europe and a primary location for events in My Hero Academia: World Heroes' Mission. It neighbors another fictional country called Klayd (クレイド Kureido?).
A group of smugglers attempt to ship chemicals used in the production of the illegal drug Trigger to Otheon, but are thwarted by Selkie, Ryukyu, Uravity, Nejire Chan, and Froppy. Selkie tells Ryukyu that the chemicals were ordered to be shipped to Otheon by a client using a fake name, and that he does not know what they were planning to do with the drugs once they reached the client. A mysterious man, later revealed to be Flect Turn, is informed of the disrupted delivery, but declares it to be fine as he already has the amount needed to prepare for the "salvation of humanity". Flect Turn later sets off a Trigger Bomb, killing hundreds of civilians. This event causes a team of heroes led by Endeavor to travel there and patrol.
- The Japanese pronunciation of Otheon closely resembles the Oseon system from Star Wars.
- The neighboring country of Klayd also references the Star Wars planet Crait.