George Jones, the definitive country singer of the last half-century, died Friday at a hospital in Nashville. He was 81.

He was hospitalized on April 18 with fever and irregular blood pressure, the Web site of Webster & Associates, his publicists, said in announcing the death.

Mr. Jones, who was nicknamed Possum for his close-set eyes and pointed nose, and later No-Show Jones for the concerts he missed during drinking and drug binges, wasa legendary figure in country music. His singing, which was universally respected and just as widely imitated, found vulnerability and doubt behind the cheerful drive of honky-tonk. With a baritone voice that was as elastic as a steel-guitar string, he brought suspense to every syllable, merging bluesy slides with the tight, quivering ornaments of Appalachian singing.

In his most memorable songs, all the pleasures of a down-home Saturday night couldn’t free him from private pain. His up-tempo songs had undercurrents of solitude, and the ballads that became his specialty were suffused with stoic desolation. “When you’re onstage or recording, you put yourself in those stories,” he once said.

As Mr. Jones sang about heartbreak and hard drinking, fans heard the echoes of a life in which success and excess battled for decades.

He bought, sold and traded dozens of houses and hundreds of cars; he made millions of dollars and lost much of it to drug use, mismanagement and divorce settlements. Through it all, he kept touring and recording, singing mournful songs that continued to ring true.

From the 1950s into the 21st century, Mr. Jones was a presence on the country charts, and as early as the 1960s he was praised by listeners and fellow musicians as the greatest living country singer. He was never a crossover act; while country fans revered him, pop and rock radio stations ignored him. But by the 1980s, Mr. Jones had come to stand for country tradition. Country singers through the decades, from Garth Brooks and Randy Travis to Toby Keith and Tim McGraw, learned licks from Mr. Jones, who never bothered to wear a cowboy hat.

“Not everybody needs to sound like a George Jones record,” Alan Jackson, the country singer and songwriter, once told an interviewer. “But that’s what I’ve always done, and I’m going to keep it that way — or try to.”

George Glenn Jones was born with a broken arm in Saratoga, Tex., an oil-field town, on Sept. 12, 1931, to George Washington and Clare Jones. His father, a truck driver and pipe fitter, bought George his first guitar when he was 9, and with help from a Sunday school teacher he taught himself to play melodies and chords. As a teenager he sang on the streets, in Pentecostal revival services and in the honky-tonks in the Gulf Coast port of Beaumont. Bus drivers let him ride free if he sang. Soon he was appearing on radio shows, forging a style modeled on Lefty Frizzell, Roy Acuff and Hank Williams.

Mr. Jones married Dorothy Bonvillion when he was 17, but divorced her before the birth of their daughter. He served in the Marines from 1950 to 1953, then signed to Starday Records, whose co-owner Pappy Daily became Mr. Jones’s producer and manager. Mr. Jones’s first single, “No Money in This Deal,” was released in 1954, the year he married his second wife, Shirley Corley. They had two sons before they divorced in 1968.

“Why Baby Why,” released in 1955, became Mr. Jones’s first hit. During the 1950s, he wrote or collaborated on many of his songs, including hits like “Just One More,” “What Am I Worth” and “Color of the Blues,” though he later gave up songwriting. In the mid-1950s he had a brief fling with rockabilly, recording as Thumper Jones and as Hank Smith. But under his own name he was a country hitmaker. He began singing at the Grand Ole Opry in 1956.

He had already become a drinker. “White Lightning,” a No. 1 country hit in 1959, required 83 takes because Mr. Jones was drinking through the session. On the road, playing one-night stands, he tore up hotel rooms and got into brawls. He also began missing shows because he was too drunk to perform.

But onstage and on recordings, his career was advancing. In 1962 he recorded one of his signature songs, “She Thinks I Still Care,” which was nominated for a Grammy Award. Another of his most lasting hits, “The Race Is On,” appeared in 1964. He was part of the first country concert at Madison Square Garden, a 10-act package in 1964 that also included Ernest Tubb, Bill Monroe and Buck Owens. At the first show of four performances Mr. Jones, who had been allotted two songs like the other acts, played five before he was carried offstage.

In 1966, Mr. Jones tried to start a country theme park in Vidor, the East Texas suburb where he lived, the first of many shaky business ventures. But there was only one performance given at the George Jones Rhythm Ranch. After singing, Mr. Jones disappeared for a month, rambling across Texas. His drinking had gotten worse. At one point his wife hid the keys to all his cars, so he drove his lawn mower into Beaumont to a liquor store — an incident he would later commemorate in a song and in music videos. Not long afterward, they were divorced.

Mr. Jones had his next No. 1 country single in 1967 with “Walk Through This World With Me.” He moved to Nashville and opened a nightclub there, Possum Holler, which lasted a few months.

He had met a rising country singer, Tammy Wynette, in 1966, and they fell in love while on tour together. She was married at the time to Don Chapel, a songwriter whose material had appeared on both of their albums. One night in 1968, Mr. Jones recalled, Ms. Wynette and Mr. Chapel were arguing in their dining room when Mr. Jones arrived; he upended the dining room table and told Ms. Wynette he loved her. She took her three children and left with Mr. Jones.

They were married in 1969 and settled in Lakeland, Fla. There, on the land around his plantation-style mansion, Mr. Jones built another country-themed park, the Old Plantation Music Park.

Mr. Jones severed his connection with Mr. Daily and later maintained that he had not received proper royalties. In 1971 he signed a contract with Epic Records, which was also Ms. Wynette’s label, and the couple began recording duets produced by Billy Sherrill, whose elaborate arrangements helped reshape the sound of Nashville. Three of Mr. Jones’s duets with Ms. Wynette — “We’re Gonna Hold On,” “Golden Ring” and “Near You” — were No. 1 country hits, an accomplishment made more poignant by the singers’ widely reported marital friction.

“Mr. and Mrs. Country Music” was painted on their tour bus. But the marriage was falling apart, unable to withstand bitter quarrels and Mr. Jones’s drinking and amphetamine use. After one fight, he was put in a straitjacket and hospitalized for 10 days. The Lakeland music park was shut down.

The couple were divorced in 1975; the two albums Mr. Jones released in 1976 were called “The Battle” and “Alone Again.” But duets by Mr. Jones and Ms. Wynette continued to be released until 1980. They made a new album, “Together Again,” in 1980, including the hit “Two Story House.” Mr. Jones and Ms. Wynette would reunite to tour and record again in the mid-1990s.

After the divorce, Mr. Jones grew increasingly erratic. He drank heavily and lost weight. His singles slipped lower on the charts. His management bounced his band members’ paychecks. At times he would sing in a Donald Duck voice onstage. And he began using cocaine and brandishing a gun; after firing at a friend’s car in 1977 he was arrested, though the charges of attempted murder were dropped.

His nickname No-Show Jones gained national circulation as he missed more engagements than he kept. When he was scheduled to play a 1977 showcase at the Bottom Line in New York, he disappeared for three weeks instead. In 1979, he missed 54 concert dates. (Later, the licenses on his cars would read ”NOSHOW1” to ”NOSHOW7.”)

But as his troubles increased, so did his fame and his album sales. “I was country music’s national drunk and drug addict,” Mr. Jones wrote in his autobiography.

Among musicians, Mr. Jones had fans outside country circles. James Taylor wrote “Bartender’s Blues” for him, and sang it with him as a duet. In 1979, on the album “My Very Special Guests,” Mr. Jones sang duets with Willie Nelson, Linda Ronstadt, Elvis Costello and Emmylou Harris. But he missed many of the recording sessions, and had to add his vocal tracks later.

Mr. Jones had moved to Florence, Ala., in part to get away from arrest warrants for nonpayment of child support to Ms. Wynette and other debts in Tennessee. In Florence, Mr. Jones had a girlfriend, Linda Welborn, from 1975 to 1981. When they broke up, she sued and won a divorce settlement under Alabama’s common-law marriage statutes.

In 1979 Mr. Jones declared bankruptcy and signed away his royalties from past and present recordings to repay his creditors. His manager was arrested for selling cocaine. That December, Mr. Jones was committed for 30 days to a drug and alcohol rehabilitation center. But he went back to cocaine and whiskey when he was released.

Yet he still had hits. “He Stopped Loving Her Today,” a song about a man whose love ends only when his life does, was released in April 1980 and began Mr. Jones’s resurgence. It was a No. 1 country hit, and the album that included it, “I Am What I Am,” sold a million copies. The Country Music Association named “He Stopped Loving Her Today” the song of the year (the award went to its songwriters, Bobby Braddock and Curly Purman), and the recording won the Grammy for best male country performance. Epic Records renewed Mr. Jones’s contract with a $500,000 advance, though most of it went to pay debts.

He became a consistent country hitmaker again, with No. 1 songs including “Still Doin’ Time” in 1981 and “I Always Get Lucky With You” in 1983. He made an album with Johnny Paycheck, a former member of his band, in 1980 and one with Merle Haggard in 1982; he recorded a single, “We Didn’t See a Thing,” with Ray Charles in 1983. And in 1984 he released “Ladies’ Choice,” an album of duets with Loretta Lynn, Brenda Lee, Emmylou Harris and other female singers.

In 1983 he married Nancy Sepulveda, who straightened out his business affairs and then Mr. Jones himself. He gave up cocaine and whiskey. The couple moved to East Texas, near Mr. Jones’s birthplace, and opened the Jones Country Music Park, which they operated for six years. He worked more steadily, although without the blockbuster successes of the early 1980s. In 1988 he changed labels again, to MCA, and soon afterward the Joneses moved to Franklin, Tenn.

By then, younger, more telegenic singers had come along with vocal styles learned largely from Mr. Jones and Merle Haggard. Now treated as an elder statesman, Mr. Jones sang duets with some of his musical heirs, including Randy Travis in 1990 and Alan Jackson in 1995. Garth Brooks, Vince Gill, Travis Tritt, Clint Black, Patty Loveless and other country stars joined Mr. Jones on the single “I Don’t Need Your Rocking Chair” in 1992. That same year he was named to the Country Music Hall of Fame.

His 1992 album, “Walls Can Fall,” sold a half-million copies. He made a duet album, “The Bradley Barn Sessions,” with country singers like Trisha Yearwood and rock musicians like Mark Knopfler and Keith Richards. In 1994, he had triple bypass surgery.

He rejoined Ms. Wynette to record an album, “One,” and to tour in 1994 and 1995, and he released an album with the same name as his autobiography, ”I Lived to Tell It All," in 1996. He changed labels, to Asylum Records, in 1998, the year that Ms. Wynette died in her sleep at the age of 55.

Until he was critically injured in an accident on March 6, 1999, when his car hit the side of a bridge while he was changing a cassette tape, Mr. Jones was performing more than 150 nights a year. A half-empty bottle of vodka was found in the car; Mr. Jones was sentenced to undergo treatment.

“Choices,” a song he released in 1999, won him a Grammy for best male country vocal. In it, he sang, “By an early age I found I liked drinkin’/ Oh, and I never turned it down.”

Mr. Jones maintained his career into the 21st century, touring steadily and recording. He was a guest vocalist on Top 30 country hits by Garth Brooks and Shooter Jennings, and he released both country and gospel albums in the early 2000s. In 2006 he and Mr. Haggard joined forces again for “Kicking Out the Footlights Again: Jones Sings Haggard, Haggard Sings Jones.” In 2012, he received a lifetime achievement Grammy Award.

The Webster & Associates Web site listed his survivors as his wife, Nancy; his sister, Helen Scroggins; and his children and grandchildren.

In his last years, Mr. Jones found himself upholding a traditional sound that had largely disappeared from commercial country radio. “They just shut us off all together at one time,” he said in a 2012 conversation with the photographer Alan Mercer. ”It’s not the right way to do these things. You just don’t take something as big as what we had and throw it away without regrets.

“They don’t care about you as a person. They don’t even know who I am in downtown Nashville.”