Baron Cohen was born into a devout Jewish family, and he studied history at the University of Cambridge (Cambridge, University of). After deciding to pursue a career in entertainment, in 1998 he joined the television comedy series The 11 O'Clock Show, for which he created the character Ali G, a “ hip-hop journalist” who was aggressively stupid. With his over-the-top attire—a brightly coloured tracksuit, tinted sunglasses, and designer skullcap—mangled English, and outlandish questions, Ali G interviewed unsuspecting actual politicians and celebrities and in the process revealed their prejudices and ignorance. His phenomenal popularity led to Da Ali G Show in 2000. Baron Cohen soon introduced two other clueless characters: Borat, a racist, anti-Semitic, homophobic, sexist Kazakh reporter, and Brüno, a gay Austrian fashion reporter. In 2001 both the show and Baron Cohen earned British Academy of Film and Television Arts awards. After making his film debut in Ali G Indahouse (2002), Baron Cohen sought new unwitting subjects, and in 2003–04 Da Ali G Show aired in the United States on the cable channel HBO.

Baron Cohen subsequently focused on his film career, and in 2005 he provided the voice of the king of the lemurs in the animated Madagascar. He next appeared as a French race-car driver opposite Will Ferrell in the comedy Talladega Nights: The Ballad of Ricky Bobby (2006). It was Borat: Cultural Learnings of America Make Benefit Glorious Nation of Kazakhstan, however, that made Baron Cohen a household name. Borat's encounters with unsuspecting Americans as he traveled across the United States provided for outrageous and often cringe-inducing moments—a gun-store owner suggests the best gun for shooting a Jew, and several fraternity brothers wish for the return of slavery. Not everyone appreciated the humour, however. Several people featured in the film sued, and the government of Kazakhstan took out newspaper ads to counter the movie's unflattering portrayal. Borat earned Baron Cohen a Golden Globe Award for best actor in a comedy, as well as an Academy Award nomination for best adapted screenplay.

Despite the controversy and Baron Cohen's high profile—which raised questions about whether he could find more unwitting participants for future projects—the movie rights to his character Brüno sold for $42.5 million in 2006. In December 2007, while promoting his work in the Tim Burton film Sweeney Todd: The Demon Barber of Fleet Street, Baron Cohen announced that he was permanently retiring the characters Borat and Ali G. His scene-stealing performance as the foil to Johnny Depp (Depp, Johnny)'s homicidal barber ensured that, even without his two best-known characters, Baron Cohen would continue to be a formidable screen presence.