Sacha Baron Cohen portrays a Kazakhstani TV reporter dispatched to the US

“Borat” is unquestionably, honestly, literally the funniest film I have ever seen.

Conceptually brilliant and fearlessly executed, it rewrites the rules of screen comedy, presenting something never before seen on film: a gene-splice of Andy Kaufman’s high-wire character humor and caught-on-the-street pranks from “Punk’d.”

The title character is a gangly, mustachioed Kazakh TV journalist traveling across “US and A,” the nation he excitedly calls “greatest country in the world.” What he finds in unstaged interviews with unsuspecting citizens is stranger than fiction, and pants-wettingly riotous. Some viewers will find their sensitivities too roughly handled, but even if you dislike it, you will find “Borat” to be a threshold experience. Five years from now, you’ll be saying, “I haven’t laughed so loud since ‘Borat,”‘ or “‘I haven’t been so offended since ‘Borat.”‘

The good-natured title character, played by British comedy phenomenon Sacha Baron Cohen, is hilariously obscene and obscenely hilarious. Borat opens the movie by offering a tour of his village, filmed in an authentic hamlet that looks like a National Geographic feature on Third World slovenliness. With pride, he shows off the kindergarten, where tots amuse themselves with automatic rifles, introduces us to his withered crone of a mother (“oldest woman in village, she 46”) and greets the “town rapist” (“naughty, naughty!”).

Packing a live chicken in his valise and taking along “a vial of Gypsy tears to protect us against AIDS,” Borat and his unkempt producer Azamat (Ken Davitian) embark on their journey in a horse-drawn Yugo.

Once on our shores, “Borat” becomes a twisted satire of international misunderstanding at its most hysterical. A poster child for precivilized politically incorrect humor, Borat follows in the footsteps of Groucho Marx, Mel Brooks and Don Rickles, mocking society with profane misbehavior. His farcical anti-Semitism and misogyny provoke smarmy earnestness from some bystanders, shocked gasps from others, a Let’s-Pretend-Nothing’s-Wrong kabuki from a few, and an appalling number of high-fives from folks who enthusiastically share his views.

What redeems the character for movie audiences is his essential sweetness and innocence, which makes the sheer delicious wrongness of his misbehavior so much the funnier. He is genuinely puzzled that a group of feminists believe women should be educated since “government scientist, Dr. Yamatov, have proved woman’s brain is size of squirrel.”

His interview goes uproariously off the tracks, but it hardly matters. What Borat really wants to ask these ladies is the address of Pamela Anderson, who “lives in place called Baywatches.” He cons Azamat into traveling to California in pursuit of his blonde dream, promising him that “Pearl Harbor is there. Also Texas.” Along the way he visits a cross-section of American society with his documentary crew.

Filming a gay rights rally in Washington, D.C., he meets many friendly gentlemen and invites them to his room for a session of traditional Kazakh underwear wrestling. At a rodeo he pumps up the patriotic crowd by wishing, “May George Bush drink the blood of every man, woman and child in Iraq!” He’s invited to a Southern mansion for a formal dinner, where he requires the flustered hostess to explain the intricacies of American flush toilets.

Every encounter is a showpiece of Cohen’s improvisational brilliance and his utter bravery as a performer. His head is in the lion’s mouth in every scene.

The movie, deliberately made to look shoddy by director Larry Charles (“Seinfeld”), is actually a remarkably slick piece of work, packed full of more throwaway visual gags than we’ve seen since the early, funny films of Woody Allen. The score, a bouncy medley of klezmer rave-ups and gypsy jazz, gives the story a rushing momentum that reaches its climax when Borat finally encounters his beloved “Pamela” and realizes the consequences of pursuing a fantasy “with plastic chest.”

Borat (Sacha Baron Cohen) mangles the national anthem at a Virginia rodeo in Borat.

What sets Cohen apart from a smirky “look at me, I’m disgusting” comic like Tom Green is his totally committed acting, and his fairness. He never breaks character, he creates his performance on the fly, and he thinks like a double-barreled satirist, using an exaggerated Polish joke caricature to send up polite Western values. He’s thoroughly convincing, enmeshing bystanders in the joke, and setting them up to deliver the punch line themselves.

This is where the fairness comes into play. Everyone who comes off looking awful in this film has done it to himself. When he enters a gun shop and asks what is the best pistol “to protect from Jew,” the owner considers a moment and replies, “I’d recommend a .45 or a 9-millimeter.”

There’s even another joke inside those multilayered jokes: Cohen’s jabbering “Kazakh” lingo is actually Hebrew slang. “Borat” is irresistibly obnoxious in any language.