Brian Cohen, played by Graham Chapman, is born in a stable adjacent to where Jesus is born, leading to a comedic mix-up for the three wise men which include John Cleese and Michael Palin. His mother, Mandy Cohen, played by Terry Jones, raises him with a strong sense of injustice. Fast forward to 33 AD, Brian becomes an idealistic young man who deeply resents the Roman occupation of Judea. His infatuation with an attractive rebel, Judith (portrayed by Sue Jones-Davies), only fuels his animosity towards the Romans, especially after learning he is half-Roman due to his mother’s traumatic past involving a Roman centurion.
As the story unfolds, Mandy and Brian find themselves attending a chaotic stoning of a man executed for uttering the word "Jehovah." In a twist of absurdity, the priest, played by John Cleese, also ends up getting hit by stones when he mentions the forbidden name. Surprisingly, women sneak into the event disguised as men to bypass the restriction on their attendance. Meanwhile, an ex-leper, portrayed by Michael Palin, harbors resentment toward Jesus for curing him and thus taking away his livelihood as a beggar.
Brian’s fervor for rebellion leads him to join the People's Front of Judea (PFJ), a disjointed group of revolutionaries, alongside characters like Reg, Francis, and Stan, who humorously longs to be recognized as Loretta. Reg commands Brian to spread the word "Romans go home" in Latin; however, Brian’s efforts backfire when he is caught by a centurion, resulting in an embarrassing lesson on proper Latin grammar.
In a failed kidnapping attempt to capture the wife of the Roman governor, Pontius Pilate (also portrayed by Michael Palin), Brian finds himself amidst conflict between the various rebel factions, leading to a hilarious mix-up as they vie for the same goal. Following a chaotic turn of events, Brian unwittingly participates in a series of confrontations with the Romans, an alien abduction, and an ill-fated quest for recognition among prophets in a bustling plaza, where he inadvertently becomes mistaken for a messiah.
As the plot thickens, a crowd starts following him, believing he holds the secrets to eternal life, leading to ridiculous scenarios involving Juniper bushes and a sage who breaks his vow of silence. After sharing a tender night with Judith, Brian discovers an enormous throng outside his mother's house, eager for his words of wisdom. Despite his pleas for independent thought, the crowd merely mimics his messages as doctrine, viewing his mother as an irritated virgin.
The PFJ quickly capitalizes on Brian’s newfound fame, demanding he provide miracle cures for their followers. In a twist of fate, Brian is captured by the Romans and sentenced to crucifixion amid Passover festivities. In a comical turn laden with irony, the crowd inadvertently mocks Pilate’s speech impediment as they frantically shout for a prisoner’s release. Eventually, Judith’s voice rises above the chaos, calling for Brian, leading to the infamous line of “Welease Bwian.”
However, a chaotic climax ensues as various crucified individuals claim to be Brian under a parody of the film Spartacus, resulting in the comedic misidentification and the wrong man being released. Despite the PFJ and Judith praising his martyrdom as hope dims, an unexpected intervention from a suicide squad hilarious gone awry gives Brian a fleeting moment of hope. Ultimately, as Brian faces his grim fate, he finds solace and uplifting spirit alongside his fellow condemned, joining them in singing >"Always Look on the Bright Side of Life."
