Brian Wilson, who as the leader and chief songwriter of the Beach Boys became rock’s poet laureate of surf-and-sun innocence, but also an embodiment of damaged genius through his struggles with mental illness and drugs, has died. He was 82.

His family announced the death on Instagram but did not say where or when he died, or state a cause. In early 2024, after the death of his wife, Melinda Wilson, business representatives for Mr. Wilson were granted a conservatorship by a California state judge, after they asserted that he had “a major neurocognitive disorder” and had been diagnosed with dementia.

On mid-1960s hits like “Surfin’ U.S.A.,” “California Girls” and “Fun, Fun, Fun,” the Beach Boys created a musical counterpart to the myth of Southern California as paradise — a soundtrack of cheerful harmonies and a boogie beat to accompany a lifestyle of youthful leisure. Cars, sex and rolling waves were the only cares.

That vision, manifested in Mr. Wilson’s crystalline vocal arrangements, helped make the Beach Boys the defining American band of the era. During its clean-cut heyday of 1962 to 1966, the group landed 13 singles in the Billboard Top 10. Three of them went to No. 1: “I Get Around,” “Help Me, Rhonda” and “Good Vibrations.”

At the same time, the round-faced, soft-spoken Mr. Wilson — who didn’t surf — became one of pop’s most gifted and idiosyncratic studio auteurs, crafting complex and innovative productions that awed his peers.

“That ear,” Bob Dylan once remarked. “I mean, Jesus, he’s got to will that to the Smithsonian.”

Mr. Wilson’s masterpiece was the 1966 album “Pet Sounds,” a wistful song cycle that he directed in elaborate recording sessions, blending the sound of a rock band with classical instrumentation and oddities like the Electro-Theremin, whose otherworldly whistle Mr. Wilson would use again on “Good Vibrations.”