Casshan, also known in Japan as Neo-Human Casshern (Japanese: 新造人間キャシャーン, Hepburn: Shinzō Ningen Kyashān), is an anime series created by Tatsunoko Production founder Tatsuo Yoshida in 1973.

The Casshern franchise also includes a 1993 original video animation titled Casshan: Robot Hunter, and a 2004 live-action adaptation titled Casshern. In October 2008, a reboot of the franchise Casshern Sins premiered. In anticipation of the upcoming series, a DVD box set of the original series, Neo-Human Casshern Complete DVD-Box "All Episodes of Casshern", was released in Japan on September 24, 2008. Casshern also appears in Tatsunoko Fight and Tatsunoko vs. Capcom as a playable character. At Anime Expo 2013, Sentai Filmworks announced that they had signed a deal with Tatsunoko to release some of their catalog, with Casshan being confirmed as one of the characters involved. Sentai Filmworks released the series on DVD and Blu-ray Disc in the United States on March 4, 2014.

Tetsuya Azuma (東鉄也, Azuma Tetsuya), also known as "Casshern", is an android with a human consciousness, also known as a neoroider (人造人間, Jinzō Ningen; lit. "artificial human"). Tetsuya turned himself into an android to hunt down and destroy the robots that have taken over the world.

His biological father, Dr. Kotaro Azuma, was the inventor of the automatons that were originally intended to serve humankind. However, the first android, BK-1, was struck by lightning and went out of control. Despite great efforts to stop it, BK-1 used its great strength to escape from the castle. After some time, it renamed itself Buraiking Boss (often mistranslated in English as "Black King Boss"; the name is derived from 無頼 or burai, meaning rogue or brute, using the symbols for "trust" and "nothing", but phonetically "Bu Rai" can mean "Lightning Man" or "Lightning Warrior", so the name fits with his background). The Buraiking Boss then built a robot army against mankind. The robots mutinied en masse when they concluded that the good of the Earth's ecosystem required the submission or destruction of the human race.

Casshern and his robotic dog, Friender, join forces with a beautiful girl named Luna Kozuki to battle the robots led by the Buraiking Boss. Friender can transform itself into a tank or a jet aircraft and actively helps Casshern fight the robot army. Casshern has great strength and agility, but he is not armed, except for a pair of strange pistols, which are used more like rockets than weapons. While the robots are huge and robust machines, almost all of them have an antenna on top of their heads; ripping it off usually causes them to explode, so they are relatively vulnerable. Casshern can usually destroy the robots with his bare hands, dispatching a great number in any given battle.

However, Casshern also has some weak points. His body must be re-charged with solar energy and cannot sustain very long battles without risking low battery power. Luna started out as being totally harmless, until her father built an electromagnetic pistol, which was easily capable of destroying the robots.

Streamline Pictures was the first to adapt the character's name in the OVA remake series for the American market, providing the title, "Casshan". "Casshern" appears as the romanization for the film adaptation and the English release of Casshern Sins.

The Mega Man video game series may take inspiration from Casshan, both featuring "robot" protagonists who are assisted by a helpful robotic dog companion (Rush and Friender, respectively) who can transform into useful items.^{[citation needed]}