Authenticity speaks for itself or not at all. Rory McIlroy seems to have it, both in his golf swing and in his face. From his understated gestures to his cocky-modest smile, from his twirl of the club as a perfect shot hangs in mid-flight to the image Sunday evening of his huge hug with his father beside the 18th green at Congressional Country Club, he makes us think, “There’s the real thing.”

Now, McIlroy is an authentic U.S. Open champion, a certified major-title winner. But he’s also something else as well — an athlete who has produced a feat so special, winning this 111th U.S. Open by eight shots with a record-setting 16-under-par score, that he must be properly placed in the history of his sport.

In 1962, ’79, ’97 and now 2011, spaced almost evenly apart, four young golfers, all either 21 or 22, and all of them preceded by enormous reputations, won their first major championship. Their names are Jack Nicklaus, Seve Ballesteros, Tiger Woods and, now, after his 65-66-68-69 — 268 victory, Northern Ireland’s McIlroy.

That’s the whole list from the last 50 years of players with prodigious early gifts, monstrous expectations and an early-career triumph that identifies them unequivocally while putting a permanent spotlight around them for the rest of their lives. Woods was 21, the others 22. They are the prodigies around whom the future of the game revolves as soon as they validate their vast potential, as McIlroy has now done beyond any doubt.

The question about these fledgling one-name golfers — Jack, Seve, Tiger and now Rory — is not whether they will go on to further glory, but just how great they will ultimately become. Nicklaus broke every record. Woods still may. The late Ballesteros, limited by back problems, still won five majors and was the Arnie of European golf.

“I know how good Tiger was in 2000. . . . I was trying to emulate him in some ways,” said McIlroy, fully aware that he’d shattered Woods’s Open scoring record by four shots, though he did it on a far easier course than Pebble Beach in ’00.

“Everyone is going to draw comparisons. It’s natural,” McIlroy added. “I’m just happy to be sitting here with a trophy that has his name on it.” (Three times.)

All week, McIlroy has concealed the size of his ambition. Surely, no one wins an Open without astronomical aspirations. Finally, McIlroy gave hints. “I was quite annoyed by the bogey at 17,” he said. “Was he bogey-free at Pebble?” “He” would be Tiger.

“I’ve watched him for 15 years. I always had thoughts to beat Tiger in a Masters or U.S. Open. So, it would be great to go down the stretch with him,” McIlroy said. “Golf is a better place with him. . . . He does bring something extra. He’s Tiger Woods.”

Sounds like “Game on,” if Woods can get healthy and back to a semblance of form.

Many will compare this McIlroy victory with Woods’s 15-shot margin to win the ’00 U.S. Open. That’s not the best analogy. That Woods win was on a truly tough Open course with vicious rough; firm, fast greens; and ocean breezes. The next-best score was 3 over. McIlroy deserves every accolade he gets for 16 under. But McIlroy shooting zero at defenseless Congressional wasn’t as impressive as ’00.

“The course did me some favors this week,” McIlroy said.

Uncooperative weather meant Congressional was neither firm nor fast. That’s nobody’s fault. The U.S. Golf Association, with hindsight, fumbled by forgetting that it’s a lot easier to cut grass if it’s too long than it is to hope that it grows exactly as much as you’d prefer. “Graduated rough,” indeed. This week’s hay just wasn’t worthy of a U.S. Open. That’s not Congressional’s fault. The USGA’s own “cost of rough” stats show that, on average, the whole field would have scored six shots higher with normally punitive Open rough.

If anything, McIlroy’s win evoked Woods at the ’97 Masters. Both were still fresh faces, instantly embraced as good for golf and capable of almost anything. Woods was long on ego, charisma and imagination; McIlroy on charm, tenacity and a flowing, high-finish swing that has the magic combination of consistent tempo and titanic distance with little apparent effort. Woods broke the Masters scoring record (18 under) and won by 12 shots. Comparing Rory’s route to Woods in ’97 is still a stretch, especially considering all the sociological weight of Woods’s win. But the two are more on the same scale.

“The two wins are very similar. They validated what everybody expected of them,” said PGA Tour Commissioner Tim Finchem, walking the course with McIlroy’s group. “In both cases, it sets the course. And it brings up the question, ‘What is that course?’ ”

How high do they fly and for how long? McIlroy certainly arrives with far less sense of mission, or historic entitlement, that surrounded Woods. On one hand, McIlroy says he’s motivated by his talks with Nicklaus, especially a lunch after his infamous Sunday 80 when he had a four-shot lead at the Masters two months ago.

“It’s nice when the most successful player that’s ever lived expects great things from you and tells you to ‘embrace the pressure,’ ” McIlroy said. But the 22-year-old, who joked about the bar still being open at his home town of Holywood, Northern Ireland, and that “probably everything is going on my account as well,” is clearly not as driven as either Woods or Nicklaus. Of winning a major at 22, he said, “I’m surprised that I’m so early.” And asked about his next major win and whether it might come this summer, McIlroy said, “If it might not be this year, that’s fine. . . . If I can add, great.”

Few victories have been surrounded by more cheers, grins and relief. “Every cloud has a silver lining,” McIlroy said of his Masters collapse and the sympathy it elicited. “It’s been a great thing for me in terms of support. It feels like a home match [here]. They cheered for me all week. It’s special for a foreigner to feel like you’re one of their own. That’ll probably be pretty important in the next few years.”

That sounds like McIlroy, or his sponsors, may think that a U.S. Open trophy means he should play more U.S. events and feed on that popularity.

McIlroy’s recent stumbles in majors have plenty of precedent. Nicklaus finished second to Arnold Palmer in the ’60 U.S. Open as a 20-year-old amateur. Ballesteros finished second in the ’76 British Open at 19, then won in ’79. Now, Rory’s early blunders are just marginalia for his biography. And that McIlroy history may be long and delicious.

Spoiler alert: The first major chapter has already been written. It ends with an enormous ovation in a hilly amphitheater at Congressional as the lowest score in 111 Opens was shot. As dusk fell, the Open record for goosebumps seemed in danger as well.