‘T HE Bachelor,” the latest and most unfortunate manifestation of Hollywood’s millennial obsession with weddings, is so unremittingly vulgar and inept it makes “The Best Man” and “Runaway Bride” look like masterpieces by comparison.

This update of Buster Keaton’s 1925 “Seven Chances” focuses on the frantic matrimonial efforts of Jimmie Shannon (Chris O’Donnell), a pool-table-company heir whose grandfather’s will leaves him $100 million – but only if he gets married by 6:05 p.m. the next day, his 30th birthday.

Keaton’s film isn’t remembered for this creaky plot gimmick but for one of the greatest sight gags in movie history – the Great Stone Face being pursued by 1,000 would-be brides in gowns after a pal tips off a newspaper to his plight.

Three-quarters of a century later, the sight of O’Donnell being chased by throngs of women through San Francisco is still good for a chuckle. But almost nothing else here works.

There’s an utter lack of chemistry between O’Donnell and his long-suffering girlfriend (an annoyingly twitchy Renee Zellweger). When she turns down his insulting marriage proposal ( “You win,” he tells her), Jimmy approaches (and is turned down by) a series of ever-more-hideously caricatured ex-girlfriends, including a feminist who dismisses his proffered roses as “symbolic vaginas.”

That not-great gag is repeated at least twice, along with every other joke in the movie – especially references to wild mustangs made by Jimmy, whose commitment problems are conveniently solved by a priest (James Cromwell) recruited to perform the quickie wedding.

Director Gary Sinyor drags out every scene and encourages all hands – including such pros as Peter Ustinov (sporting a horrible Southern accent), Ed Asner and Hal Holbrook – to overact with abandon.

The most excruciating moments in “The Bachelor” belong to Brooke Shields, transcendently awful as a financially distressed socialite who contemplates marrying Jimmy for money. She’s lit, photographed and costumed so badly that she – along with Mariah Carey, who turns up briefly as an opera singer – bears an unfortunate resemblance to a drag queen.