The English fighter, who is almost a household figure in his native country, takes his performance to America. Anthony Joshua is a British aristocrat, a prizefighting clotheshorse from London who is thirty-four years old and has four heavyweight title belts in his wardrobe.

Mr. Joshua is 6 feet 6 inches tall, weighs 250 pounds, and has the body fat of lettuce. He is ridiculously gorgeous for a man whose job entails taking hits to the face, and he has an unblemished record (22-0, 21 knockouts). According to a 2018 Forbes list of the world’s highest-paid athletes, he also has a portfolio worth $39 million, which is practically unheard-of for a boxer who hasn’t competed professionally in the US.

Anthony Joshua at a training session in Sheffield, England, this month.

Mr. Joshua’s net worth has undoubtedly expanded as a result of business arrangements he has secured with 14 predominantly European “commercial partners” in recent years. Additionally, he inked a multimillion-dollar deal with DAZN.

Though Mr. Joshua is wildly popular in London, where 90,000 fans roar when he trades punches with opponents at Wembley Stadium, his recent arrival at a Hugo Boss store in Midtown Manhattan was met with the kind of notice that could be appreciated only by a cat burglar. Nary a soul knew the champ was in the house.

“I wouldn’t expect anyone outside of boxing to recognize me in New York, or any other place in the world where they haven’t seen me fight,” Mr. Joshua said early in May at the Hugo Boss Columbus Circle location. There he inspected several new pieces created for the Boss Stretch Tailoring campaign, which Mr. Joshua began endorsing about a year and a half ago.

Mr. Joshua visiting the Hugo Boss store at Columbus Circle in New York.

“You like this jacket?” Mr. Joshua asked, rolling a dark blue sports jacket over his broad shoulders. “I helped design it. It’s not too loud, but rather simple and clean and pretty sharp overall — kind of like me.”

His unceremonious greeting at the shop appeared to catch the affable boxer with his guard down. Yet it was an indication that Mr. Joshua suffers from an American identity crisis that could derail the expansion of his financial empire in the United States, where he is banking on becoming boxing’s version of David Beckham, whom Mr. Joshua refers to as his “style icon.” (Mr. Beckham has earned an estimated $800 million in his lifetime, according to Forbes.)

Bill Duffy, a sports agent who represents past and current N.B.A. players, including Yao Ming, the 7-foot-6-inch former Houston Rocket by way of Shanghai who had a Hall of Fame career in the early 2000s, and Luka Doncic, a Slovenian-born rising star with the Dallas Mavericks, said Mr. Joshua’s goal of achieving Beckham-like wealth and fame through boxing will not be easy.

“Beckham is one of the few non-American athletes I’ve seen crack the code and capture the American marketplace at a really high level,” said Mr. Duffy, who drew a comparison between Mr. Ming, once an unknown in America, and Mr. Joshua.

“Yao Ming was already a star in China but somewhat of a mystery when he came to the United States, and while Joshua may be a star in England, I know he’s a mystery here because I never heard of him,” Mr. Duffy said. “But when Yao began performing at an All-Star level in America, that’s what validated him. That’s what stamped him as a global icon.”

“If Joshua comes over here and starts kicking some butt,” Mr. Duffy added, “he will also get that same kind of validation, that same kind of recognition.”

Freddie Cunningham, Mr. Joshua’s managing director, is well aware of the importance of his fight with Mr. Ruiz, who will be attempting to take home Mr. Joshua’s W.B.A., W.B.O., I.B.F. and I.B.O. titles, not to mention the multi-million-dollar purse.

“This is simply a must-win situation,” Mr. Cunningham said. “In order to please both the American audience and potential commercial partners here in the United States, Anthony must not just win this fight, but he must win it in style.”

Mr. Joshua, who was on the cover of British GQ magazine — he was voted its Sportsman of the Year in 2017 — has combined good looks with great entrepreneurial instincts to become a marketing machine whose image is used to sell clothing, jewelry, automobiles and other products throughout England.

Mr. Joshua in the Boss Stretch Tailoring ad campaign.

During his undefeated run as a professional fighter, which followed his gold medal performance as a member of Britain’s boxing team at the 2012 Olympics, he has entered into business deals with such companies as Hugo Boss, Under Armour and Jaguar Land Rover.

“I have a four-to-five-year American plan,” Mr. Joshua said, as he tried on another jacket. “During that time, I will fight as often as I can in the United States, and I will put on such memorable performances that people here, or anywhere, will never forget my name.”

“I will be wearing all four of my belts when I step into the ring to fight Ruiz, and all four when I leave the ring that night,” said Mr. Joshua, his oversize grin reflecting in an undersized mirror he used to try on the new clothing.

Mr. Joshua, a single father living in Golders Green, a tiny suburb of London, is helping to raise his 3-year-old son, Joseph, in a rather comfortable environment these days. (Joseph also lives with his mother part of the time.) And yet, for all he has achieved in London, Mr. Joshua “cannot afford to have an off night in New York on June 1,” he said, “if I want people here to know my name.”

“Putting forth a boring effort, even in victory, would not be the proper way to introduce myself to an American audience in a place like Madison Square Garden, where Ali fought Frazier, where Frank Sinatra sang, where legends were made.