Charles T. Munger, who quit a well-established law career to be Warren E. Buffett’s partner and maxim-spouting alter-ego as they transformed a foundering New England textile company into the spectacularly successful investment firm Berkshire Hathaway, died on Tuesday in Santa Barbara, Calif. He was 99.

His death, at a hospital, was announced by Berkshire Hathaway. He had a home in Los Angeles.

Although overshadowed by Mr. Buffett, who relished the spotlight, Mr. Munger, a billionaire in his own right — Forbes listed his fortune as $2.6 billion this year — had far more influence at Berkshire than his title of vice chairman suggested.

Mr. Buffett has described him as the originator of Berkshire Hathaway’s investing approach. “The blueprint he gave me was simple: Forget what you know about buying fair businesses at wonderful prices; instead, buy wonderful businesses at fair prices,” Mr. Buffett once wrote in an annual report.

That investing strategy was a revelation for Mr. Buffett, who had made his name in the 1950s buying troubled companies at deep discounts. (He called them “cigar butts,” because investing in them, he said, was like “picking up a discarded cigar butt that had one puff remaining in it.”)

Mr. Munger counseled Mr. Buffett that if he wanted to build a large, sustainable company that would outperform other investors, he should buy solid brand-name companies. “He was the architect and I was the general contractor,” Mr. Buffett said of their relationship.

The partnership, spanning more than 50 years, produced one of the most successful and largest conglomerates in history. Among other properties, Berkshire, which is based in Omaha, owns the insurance giant Geico and the Burlington Northern Santa Fe railroad company and holds stakes in Coca-Cola, American Express, IBM, Wells Fargo and other corporate heavyweights. By 2022 it had about 372,000 employees.

Mr. Munger, an erudite man who sprinkled his conversations with references to Cicero, Albert Einstein, Mark Twain and Confucius, was widely known for his witty common-sense maxims, so much so that they were called Mungerisms and collected in books, including “Poor Charlie’s Almanack: The Wit and Wisdom of Charles T. Munger” (2005).

“Envy is a really stupid sin,” goes one, “because it’s the only one you could never possibly have any fun at.” Another: “The ethos of not fooling yourself is one of the best you could possibly have. It’s powerful because it’s so rare.”

Mr. Buffett and Mr. Munger would talk to each other on the telephone for hours every day, Mr. Buffett from his office in Omaha (their mutual hometown) and Mr. Munger from Los Angeles.

“We’ve never had an argument,” Mr. Buffett said. Repeating one of Mr. Munger’s favorite lines, Mr. Buffett said that when they did differ, Mr. Munger would say, “Warren, think it over and you’ll agree with me because you’re smart and I’m right.”

Mr. Buffett and Mr. Munger were the faces of Berkshire’s annual meeting in Omaha, what became known as the Woodstock of Capitalism. They would hold forth in front of tens of thousands of rapt Berkshire shareholders, answering questions for up to six hours and dispensing their investment wisdom.

“The trouble with making all these pronouncements is people gradually begin to think they know something,” Mr. Munger told the audience in 2015. “It’s much better to think you’re ignorant.” He added, “If people weren’t so often wrong, we wouldn’t be so rich.”

Many of those listeners had become vastly wealthy themselves by investing with Mr. Buffett and Mr. Munger. A $1,000 investment in Berkshire made in 1964 is worth more than $10 million today.

Mr. Munger was often viewed as the moral compass of Berkshire Hathaway, advising Mr. Buffett on personnel issues as well as investments. His hiring policy: “Trust first, ability second.”

A Lawyer’s Son

Charles Thomas Munger was born in Omaha on Jan. 1. 1924, the son of Alfred Case Munger, a lawyer, and Florence (Russell) Munger. As a boy he worked Saturdays in a grocery store then owned by Mr. Buffett’s grandfather. (Mr. Buffett worked there for a time himself, but the two did not meet until much later.) At 17, Charles went to the University of Michigan to major in mathematics, but in his sophomore year, after the attack on Pearl Harbor, he enlisted in the Army Air Corps.

Promoted to second lieutenant, he was dispatched to the California Institute of Technology in Pasadena to train as a meteorologist. In Pasadena he met Nancy Huggins, daughter of a local shoe store owner, and they married, he at 21 and she at 19. They went on to have three children.

Soon he was assigned to Nome, Alaska, where he developed a talent that would serve him well.

“Playing poker in the Army and as a young lawyer honed my business skills,” Mr. Munger told Janet Lowe in her 2000 book “Damn Right! Behind the Scenes with Berkshire Hathaway Billionaire Charlie Munger.”

“What you have to learn is to fold early when the odds are against you,” he said, “or if you have a big edge, back it heavily, because you don’t get a big edge often, so seize it when it does come.

Even before his discharge from the Army in 1946, Mr. Munger, who once said he had a black belt in chutzpah, applied to Harvard Law School, from which his father had graduated, even though he had desultory work habits and no undergraduate degree. He was accepted only after intervention by a fellow Nebraskan, Roscoe Pound, a retired dean of the school and a family friend.

Graduating with honors, Mr. Munger returned to California and began practicing law. He eventually struck out on his own by founding the law firm Munger, Tolles & Olson. But his life had begun to unravel: He and his wife divorced; their only son, Teddy, died of leukemia at 9 years old; and he suffered financial reverses.

With Mr. Munger practically broke, his daughter Molly complained to him about his beat-up yellow Pontiac. “Daddy, this car is just awful, a mess,” she said. “Why do you drive it?” As recounted in Ms. Lowe’s biography, he replied, “To discourage gold diggers.”

Seeking to rebuild, and drawing on his preternatural math skills (“I always took math courses because I could get an ‘A’ without doing any work,” he said), he began investing on the side, in stocks, businesses and real estate.

“It soon occurred to me that I’d rather be one of our rich and interesting clients than be their lawyer,” he said.

His investments generated his first million dollars.

Mr. Munger married Nancy Barry Borthwick in 1956, and he met Mr. Buffett by happenstance three years later. Mr. Munger had flown back to Omaha to organize the affairs of his recently deceased father when he was invited to lunch at the local Omaha Club. There he was introduced to Mr. Buffett by a mutual friend.

Later that week, Mr. Munger attended a dinner party to which Mr. Buffett had also been invited. They hit it off and spent the evening talking. Mr. Buffett later recalled, “He was rolling on the floor laughing at his own jokes, and I thought, ‘That is my kind of guy.’ I do the same thing.”

Days later, they and their wives went to lunch at Johnny’s Cafe.

As quoted in “The Snowball,” Alice Schroeder’s 2008 biography of Mr. Buffett, Nancy Munger at one point asked her husband, “Why are you paying so much attention to him?” Mr. Munger replied: “You don’t understand. That is no ordinary human being.”

‘A Passion to Get Rich’

The men soon found themselves on the phone nearly every day talking about investing strategies. “Warren obviously had a better business model than I did,” Mr. Munger said, referring to his billing by the hour for his legal services. “He kept pointing out to me that I had an insane way of making a living, and that his was better and that I should do what he was doing.”

Mr. Munger was won over. “Like Warren, I had a considerable passion to get rich,” Mr. Munger was quoted as saying in Roger Lowenstein’s book “Buffett: The Making of an American Capitalist” (1995). “Not because I wanted Ferraris — I wanted the independence. I desperately wanted it. I thought it was undignified to have to send invoices to other people.”

Mr. Munger began investing side by side with Mr. Buffett, in companies like Westco Financial and See’s Candies, before officially joining him as vice chairman. For the first year, he said, “I kept one toe in the law firm in case my capitalist career cratered.”

Together they built Berkshire into a $500 billion-plus juggernaut whose original shares posted annual gains averaging 21.6 percent between 1965 and 2014, more than twice the 9.9 percent rise for the Standard & Poor’s 500. (Mr. Buffett got his start by taking over a fading textile manufacturer, Berkshire Hathaway, in New Bedford, Mass.)

The money Mr. Munger made far surpassed his greatest expectations, he said, but it could have been even more. He said his biggest mistakes were not bad investments, but investments Berkshire failed to make.

He and Mr. Buffett “were offered a stake in McDonald’s way early” and decided against it, he said.

“We should have bought a big block of Wal-Mart young,” he added. “That was billions that we should’ve made. We avoided the pharmaceutical industry entirely, and it was the easiest industry to make a lot of money out of all the ones around, and we never made a nickel out of it.”

Mr. Munger used his many nickels for an unusual philanthropic passion: architecture. He gave away hundreds of millions of dollars to university architecture projects, including $65 million for the Kavli Institute for Theoretical Physics at the University of California, Santa Barbara.

At least one of his projects caused controversy: His design for a windowless dorm room building at the Santa Barbara campus, for which he contributed $200 million, was criticized by some architects and students. He defended it as efficient and effective.

Active Into His 90s

Mr. Buffett remained a vocal proponent of philanthropy through his Giving Pledge, an organization he founded with Bill and Melinda Gates to persuade billionaires to give away at least half their fortunes. But Mr. Munger was conspicuously not on the list. He said it was not that he did not want to sign the pledge. He said his wife, Nancy, who died in 2010 at 86, had wanted her half of the estate passed to the children, “and so I more than did that.” He added: “I felt it would be hypocritical for me to be a big pledger. I’ve already violated the total spirit of it.”

Mr. Munger is survived by two daughters from his first marriage, Wendy and Molly Munger; a daughter from his second marriage, Emilie Munger Ogden; three sons from that marriage, Charles Jr., Barry and Philip; two stepsons, William and David Borthwick; 15 grandchildren; and seven great-grandchildren.

A treasured retreat of his was a northern Minnesota wilderness compound on Star Island in Cass Lake, where his grandparents began summering in 1932 and which became the extended-family seat. In addition to Los Angeles, he had a home Hawaii.

Under Mr. Buffett and Mr. Munger, Berkshire invested heavily in newspapers, among them The Washington Post, The Buffalo News and The Omaha World-Herald. Mr. Munger himself was the chairman of the Daily Journal Corporation, a newspaper publisher, from 1977 to 2022.

He remained active in Berkshire Hathaway into his 90s while serving for decades as chairman of Good Samaritan Hospital in Los Angeles, to which he lavishly donated. A Republican, he was also outspoken in support of Planned Parenthood.

Perhaps in another life Mr. Munger, with all his drive and self-assurance, would have been the chief of a giant corporation. But he had no regrets about making his fortune in the shadow of Mr. Buffett.

“I didn’t mind at all playing second fiddle to Warren,” he said in an interview for this obituary. “Ordinarily, everywhere I go I am very dominant, but when somebody else is better, I’m willing to play the second fiddle. It’s just that I was seldom in that position, except with Warren. But I didn’t mind it at all.”

Alex Traub contributed reporting.