AFTER a super-speed romance, PARIS HILTON pops question to toy boy River Viiperi.

That’s right! The notorious party princess, 31, says she’s ready to settle down with the dashing Spanish model, 21,her constant companion since the two fell hard for each other during New York’s Fashion Week in September, say sources.

“Paris asked for River’s hand because so many of her friends are engaged or already married with kids, and she didn’t want to be some sad, old loser left on the shelf,” revealed a pal. “It’s incredibly impulsive because they’ve only been together a few months, but Paris believes River is the one.

“He’s given her an enthusiastic yes, but they’re keeping the engagement quiet for now.”

Sources say River is perfect for the hotel heiress, who’s most famous for her defunct reality show “The Simple Life,” an embarrassing sex tape, several arrests and jet-setting around the globe to attend glitzy parties. As The ENQUIRER reported, Paris most recently made waves when she was blasted by screen legend Robert Redford for acting up at his Sun­dance Film Festival in January.

Meanwhile, friends say River loves Paris’ diva attitude, doesn’t mind taking a back seat to her and is mature beyond his years.

“Paris can see he’s a good influence,” said another insider. “He’s very easygoing and knows how to calm her down when something annoys her.”

Paris is seemingly set to settle down because she realizes that her high-profile days as the world’s No. 1 party girl are fading fast.

“She feels her wild-child days are behind her and wants the comfort that comes with marriage,” disclosed her pal.

Paris has reportedly been engaged at least twice in the past and has dated a phone book full of hunks, including actor Leonardo DiCaprio and online gambling entrepreneur Rick Salomon, her partner in her scandalous porn video “1 Night in Paris.”

“Paris feels she has finally found Mr. Right,” said the pal, “even if he is a decade younger.”