He was portrayed by the late John Neville.
Baron Münchhausen is a brave and arrogant nobleman who is always in search of adventure. He is easily distracted by beautiful women, and will at times even ignore important duties when he is showed attention by women. He is possesses the ability to grow younger when dancing with a young woman. Perhaps because of his noble upbringing, he is at times very rude to his companions, who rarely seem to tske offense to his mistreatment. Though he constantly exaggerates his life events, he seems not to recognize his embellishment, prideing himself an honest man. He is likely delusional. Though he will not demonstrate it openly, Münchhausen has a soft spot for children, especially Sally, a theatre owner's daughter who stowes away to help in his adventure and keep him on track. He has a pet dog named Argus, and a white horse named Bucephalus, both of whome he holds in high esteem. He considers himself an enemy of reason, and prefers to solve his problems with imaginative interventions rather than logical ones.
The Baron first appears when he crashes a play about his adventures put on by Henry Salt and his traveling theatre troupe, protesting its inaccuracies. He then vows to save the unnamed Prussian town that the play is being performed in from its ongoing war with Turkey. He claims that it was he who caused the Sultan to attack, when he won a wager, and as per the terms of the wager, left the Sultan's treasury with all the wealth that his strongest man could carry. Unfortunately for the Sultan, Münchhausen had Albrecht, a man with superhuman strength in his employ. He completely cleans out the Sultan's treasury, infuriating the grand Turk and inspiring him to wage war. The city's chief official, the Right Ordinary Horatio Jackson finds the Baron's warning ridiculous, and orders him arrested, but before he can be detained, Münchausen escapes in a balloon made from women's undergarments. Unbeknownst to him, the theater owner's daughter Sally Salt, the one person in the city who believed him, stowes away with him.
He soon arrives on the moon to free his friend Berthold who has been held captive for decades. Unfortunately he runs afoul the delusional and power mad king of the moon, who locks he and Sally away in a giant birdcage to keep him out of his way. The Baron meets up with Berthold, who he rescues from his imprisonment with the assistance of the queen of the moon, who he managed to charm in previous adventures. When the moon's king learns of his wife's betrayal, he is infuriated, and vows to kill the Baron and his friends. The three manage to outsmart the king and destroy his body, leaving him just a head who is propelled into space when he sneezes.
The Baron and his friends fall off the moon and land in the mouth of a giant volcano, the lair of Vulcan. He has taken Albrecht, the strong man of Münchausen's former employ, as his man servant. Albrecht likes being treated like a dainty servant, and doesn't want to leave, but he is soon given no choice when Vulcan ejects him and the rest of the Baron's companions from his lair after a frustrated Sally reveals to Vulcan that the Baron has been dancing with his wife, Venus.
Münchausen and his friends are swallowed by a giant angler fish, and inside the fish they meet his final two companions, Adolphus, with superhuman eyesight and perfect accuracy with a rifle, and Gustavus, a dwarf with superhuman hearing, who can create powerful winds when he blows out air, along with his faithful steed Bacephalus. Adolphus and Gustavus have given up hope of ever escaping and their abilities have dulled horribly with age and disuse. Sally scolds the Baron for giving up, and he is reinvigorated. The Baron blows a handful of snuff into the fish's sinus cavity, causing it to sneeze he and his companions up.
The Baron lifts himself and his horse from the water by pulling his own ponytail. He tries to inspire his companions to fight the Sultan's army and restore peace, but they are all too old and tired, so the Baron resigns to surrender himself in the name of peace. His act of selfless heroism finally inspires his cohorts to fight back. With the help of his friends still impressive abilities, as well as Sally and his faithful steed, Münchhausen defeats the Sultan and Jackson, sending the latter into hiding.
On his triumphant return to the city, Baron Münchhausen is assassinated by Horatio Jackson, causing grief and sadness throughout the city, but this was revealed to just be part of the story, and Münchhausen manages to rally the citizens to rebel against Jackson and open the gate to the city walls, revealing that the war has indeed ended. The Baron waves goodbye and throws a rose to his friend Sally, before riding away on Bacephalus, with Argus close in toe.