SINGAPORE — Lee Kuan Yew, who transformed the tiny outpost of Singapore into one of Asia’s wealthiest and least corrupt countries as its founding father and first prime minister, died here on Monday. He was 91.

His death, at the Singapore General Hospital, was announced by Prime Minister Lee Hsien Loong, Mr. Lee’s eldest son.

Mr. Lee was prime minister from 1959, whenSingapore gained full self-government from the British, until 1990, when he stepped down. Late into his life he remained the dominant personality and driving force in what he called a First World oasis in a Third World region.

The nation reflected the man: efficient, unsentimental, incorrupt, inventive, forward-looking and pragmatic.

“We are ideology-free,” Mr. Lee said in an interviewwith The New York Times in 2007, stating what had become, in effect, Singapore’s ideology. “Does it work? If it works, let’s try it. If it’s fine, let’s continue it. If it doesn’t work, toss it out, try another one.”

His leadership was criticized for suppressing freedom, but the formula succeeded. Singapore became an admired international business and financial center.

An election in 2011 marked the end of the Lee Kuan Yew era, with a voter revolt against the ruling People’s Action Party. Mr. Lee resigned from the specially created post of minister mentor and stepped into the background as the nation began exploring the possibilities of a more engaged and less autocratic government.

Since Singapore separated from Malaysia in 1965 — an event Mr. Lee called his “moment of anguish” — he had seen himself in a never-ending struggle to overcome the nation’s lack of natural resources, a potentially hostile international environment and a volatile ethnic mix of Chinese, Malays and Indians.

“To understand Singapore and why it is what it is, you’ve got to start off with the fact that it’s not supposed to exist and cannot exist,” he said in the 2007 interview. “To begin with, we don’t have the ingredients of a nation, the elementary factors: a homogeneous population, common language, common culture and common destiny. So, history is a long time. I’ve done my bit.”

His “Singapore model” included centralized power, clean government and economic liberalism. But it was also criticized as a soft form of authoritarianism, suppressing political opposition, imposing strict limits on free speech and public assembly, and creating a climate of caution and self-censorship. The model has been studied by leaders elsewhere in Asia, including China, and the subject of many academic case studies.

Prime Minister Lee Kuan Yew addresses a crowd in Singapore in 1964. He was the nation’s dominant personality for many years. CreditAssociated Press

The commentator Cherian George described Mr. Lee’s leadership as “a unique combination of charisma and fear.”

As Mr. Lee’s influence waned, the questions were how much and how fast his model might change in the hands of a new, possibly more liberal generation. Some even asked, as he often had, whether Singapore, a nation of 5.6 million, could survive in a turbulent future.

Mr. Lee was a master of so-called “Asian values,” in which the good of society takes precedence over the rights of the individual and citizens cede some autonomy in return for paternalistic rule.

Generally passive in political affairs, Singaporeans sometimes chide themselves as being overly preoccupied with a comfortable lifestyle, which they sum up as the “Five C’s” — cash, condo, car, credit card, country club.

In recent years, though, a confrontational world of political websites and blogs has given new voice to critics of Mr. Lee and his system.

Even among people who knew little of Singapore, Mr. Lee was famous for his national self-improvement campaigns, which urged people to do such things as smile, speak good English and flush the toilet, but never to spit, chew gum or throw garbage off balconies.

“They laughed, at us,” he said in the second volume of his memoirs, “From Third World to First: The Singapore Story 1965-2000.” “But I was confident that we would have the last laugh. We would have been a grosser, ruder, cruder society had we not made these efforts.”

Mr. Lee developed a distinctive Singaporean mechanism of political control, filing libel suits that sometimes drove his opponents into bankruptcy and doing battle with critics in the foreign press. Several foreign publications, including The International Herald Tribune, which is now called The International New York Times, have apologized and paid fines to settle libel suits.

The lawsuits challenged accusations of nepotism — members of Mr. Lee’s family hold influential positions in Singapore — and questions about the independence of the judiciary, which its critics say follows the lead of the executive branch.

Mr. Lee denied that the suits had a political purpose, saying they were essential to clearing his name of false accusations.

He seemed to believe that criticism would gain currency if it were not challenged vigorously. But the lawsuits themselves did as much as anything to diminish his reputation.

Mr. Lee was proud to describe himself as a political street fighter more feared than loved.

“Nobody doubts that if you take me on, I will put on knuckle-dusters and catch you in a cul-de-sac,” he said in 1994. “If you think you can hurt me more than I can hurt you, try. There is no other way you can govern a Chinese society.”

A jittery public avoided openly criticizing Mr. Lee and his government and generally obeyed its dictates.

“Singaporeans are like a flea,” said Mr. Lee’s political tormentor, J.B. Jeyaretnam, who was financially broken by libel suits but persisted in opposition until his death in 2008. “They are trained to jump so high and no farther. Once they go higher they’re slapped down.”

In an interview in 2005, Mr. Jeyaretnam added: “There’s a climate of fear in Singapore. People are just simply afraid. They feel it everywhere. And because they’re afraid they feel they can’t do anything.”

Mr. Lee’s vehicle of power was the People’s Action Party, or P.A.P., which exercised the advantages of office to overwhelm and intimidate opponents. It embraced into its ranks the nation’s brightest young stars, creating what was, in effect, a one-party state.

To remove the temptation for corruption, Singapore linked the salaries of ministers, judges and top civil servants to those of leading professionals in the private sector, making them some of the highest-paid government officials in the world.

It was only in 1981, 16 years after independence, that Mr. Jeyaretnam won the first opposition seat in Parliament, infuriating Mr. Lee. Two decades later, after the 2006 election, just two of the Parliament’s 84 elected seats were held by members of opposition parties.

But in 2011, the opposition won an unprecedented six seats, along with an unusually high popular vote of close to 40 percent, in what was seen as a demand by voters for more accountability and responsiveness in its leaders. Pragmatic as always, the P.A.P. reacted by modifying its peremptory style and acknowledging that times were changing.

But the new approach still fell short of true multiparty democracy, and Singaporeans continued to question whether the party intended to change itself or would even be able to do so.

“Many people say, ‘Why don’t we open up, then you have two big parties and one party always ready to take over?’ “ Mr. Lee said in a speech in 2008. “I do not believe that for a single moment.”

He added: “We do not have the numbers to ensure that we’ll always have an A Team and an alternative A Team. I’ve tried it; it’s just not possible.”

What Singapore got was centralized, efficient policy making and social campaigns unencumbered by what Mr. Lee called the “heat and dust” of political clashes.

One government campaign tried to combat a falling birthrate by organizing, in effect, an official matchmaking agency aimed particularly at affluent ethnic Chinese.

Mr. Lee also promoted the use of English as the language of business and the common tongue among the ethnic groups, while recognizing Malay, Chinese and Tamil as other official languages.

With tourists and investors in mind, Singapore sought to become a cultural and recreational hub, with a sprawling performing arts center, museums, galleries, Western and Chinese orchestras and not one but two casinos.

Despite his success, Mr. Lee said that he sometimes had trouble sleeping and that he calmed himself each night with 20 minutes of meditation, reciting a mantra: “Ma-Ra-Na-Tha.”

“The problem is to keep the monkey mind from running off into all kinds of thoughts,” he said in an interview with The Times in 2010. “A certain tranquillity settles over you. The day’s pressures and worries are pushed out. Then there’s less problem sleeping.”

Lee Kuan Yew, who was sometimes known by his English name, Harry Lee, was born in Singapore on Sept. 16, 1923, to a fourth-generation, middle-class Chinese family.

He worked as a translator and engaged in black market trading during the Japanese occupation in World War II, then went to Britain, where he earned a law degree in 1949 from Cambridge University. In 1950 he married Kwa Geok Choo, a fellow law student from Singapore. She died in 2010.

After serving as prime minister from 1959 to 1990, Mr. Lee was followed by two handpicked successors, Goh Chok Tong and Mr. Lee’s eldest son, Lee Hsien Loong. Groomed for the job, the younger Mr. Lee has been prime minister since 2004.

Besides the prime minister, Mr. Lee is survived by his younger son, Lee Hsien Yang, who is the chairman of the Civil Aviation Authority of Singapore; a daughter, Dr. Lee Wei Ling, who runs the National Neuroscience Institute; a younger brother, Suan Yew; and a younger sister, Monica.

Ho Ching, the wife of the prime minister, is executive director and chief executive of Temasek Holdings, a government holding company.

“His stature is immense,” Catherine Lim, a novelist and frequent critic of Mr. Lee, said in an interview. “This man is a statesman. He is probably too big for Singapore, on a level with Tito and de Gaulle. If they had three Lee Kuan Yews in Africa, that continent wouldn’t be in such a bad state.”

The cost of his success, she said, was a lack of emotional connection.

“Everything goes tick-tock, tick-tock,” she said. “He is an admirable man, but, oh, people like a little bit of heart as well as head. He is all hard-wired.”

In the 2010 interview with The Times, though, he took a reflective, valedictory tone.

“I’m not saying that everything I did was right, but everything I did was for an honorable purpose,” he said. “I had to do some nasty things, locking fellows up without trial.”

He said that he was not a religious man and that he dealt with setbacks by simply telling himself, “Well, life is just like that.”

Mr. Lee maintained a careful diet and exercised for most of his life, but he admitted to feeling the signs of age and to a touch of weariness at the self-imposed rigor of his life.

“I’m reaching 87, trying to keep fit, presenting a vigorous figure, and it’s an effort, and is it worth the effort?” he said. “I laugh at myself trying to keep a bold front. It’s become my habit. So I just carry on.”

CREDIT: THE NEW YORK TIMES SETH MYDANS