Frederick Crews, who brought a heady combination of research, wit and scholarly vinegar to his literary criticism and essays, skewering trends in academic writing and relentlessly challenging the legacy of Sigmund Freud, died June 21 at a hospital in Oakland, Calif. He was 91.

His wife, Elizabeth Crews, confirmed the death but did not cite a cause.

A longtime English professor at the University of California at Berkeley, Dr. Crews cast himself as a perpetual skeptic, questioning unsupported theories, fads and traditions while ranging through the thickets of literature and culture.

He wrote more than a dozen books, including “The Random House Handbook” (1974), an elegant style manual for writers, and was a regular contributor to the New York Review of Books, where he explored the work of Melville, Kafka and Faulkner while writing critical takedowns of theosophy, creationism, UFO abduction stories and the Rorschach test.

The fact that some of his targets had plenty of well-credentialed supporters, including among academics, only spurred him on.

“That’s what really engages me: the abdication of common sense by people who have been given every opportunity to educate themselves in rational principles, but who consider rationality itself to be old hat,” he told the Berkeley Daily Planet in 2006.

Dr. Crews first attracted national attention with “The Pooh Perplex” (1963), a merciless sendup of highbrow literary criticism. Purporting to tell readers the truth behind the Winnie-the-Pooh books, it lampooned Marxist, Freudian and New Criticism approaches through mock essays like “A Bourgeois Writer’s Proletarian Fables” and “A.A. Milne’s Honey-Balloon-Pit-Gun-Tail-Bathtubcomplex.”

The book became an unexpected bestseller and was followed nearly four decades later by a spiritual sequel, “Postmodern Pooh” (2001), parodying a new wave of academic trends. An essay on the biopoetics of the Hundred Acre Woods included a chart illustrating the “Stochastic teddy bear descent rate” as Pooh plummets from a tree into a bush.

By then, Dr. Crews was perhaps best known for his work on psychoanalysis, first as a disciple and then as a critic — one of the most prominent of the “Freud bashers” who took a sledgehammer to the Viennese physician’s legacy and work.

Fascinated by Freud’s writings on the complexity of the human psyche and the role of the unconscious mind, Dr. Crews had applied a psychoanalytic approach to literary criticism at the outset of his career, including in a 1966 study of author Nathaniel Hawthorne. But over the next decade, he soured on psychoanalysis, concluding that Freud had used circular reasoning and misrepresented the outcome of his cases while founding a “respectable and entrenched pseudoscience.”

“Our great detective of the unconscious was incompetent from the outset — no more astute, really, than Peter Sellers’ bumbling Inspector Clouseau,” he wrote.

Dr. Crews aired his doubts in the essay collections “Out of My System” (1975) and “Skeptical Engagements” (1986), then launched a full-fledged assault on Freudianism with a 10,000-word article, “The Unknown Freud” (1993), published in the New York Review of Books. The next year, he followed it up with a two-part attack on the recovered-memory movement, in which therapists claimed to have dug up memories of long-repressed abuses that patients experienced in early childhood.

Collectively, the Freud and memory essays “triggered one of the most rancorous highbrow free-for-alls ever run in a paper that has published its share of them,” literary critic Louis Menand later wrote in the New Yorker. “Letters of supreme huffiness poured into the Review, the writers lamenting that considerations of space prevented them from pointing out more than a handful of Crews’s errors and misrepresentations, and then proceeding to take up many column inches enumerating them.”

Elizabeth Loftus, a psychologist and memory expert at the University of California at Irvine, credited Dr. Crews with helping turn the tide against recovered-memory therapy, which helped fuel the “satanic panic” of the 1980s and ’90s. During that period, patients had accused therapists such as Bennett Braun of spawning false memories of devil worship and child sex abuse, eventually winning multimillion-dollar court settlements.

“We were in the trenches together,” Loftus said of her and Dr. Crews’s campaign in “the memory wars,” a term he used as the title of a 1995 book.

“He was very mild-mannered, very gentlemanly,” she added in a phone interview. “That personality didn’t quite match how sardonic he could be, and the wittiness of the kinds of things he would say in his writings about people he thought were basically idiots.”

Dr. Crews was a two-time finalist for the National Book Critics Circle Award for criticism, for the essay collections “The Critics Bear It Away” (1992) and “Follies of the Wise” (2006), which featured many of his New York Review of Books pieces. He continued to challenge psychotherapy in books including “Freud: The Making of an Illusion” (2017), a lacerating, heavily researched biographical study that tied together scholarship on the psychoanalyst’s life and work.

Critics admired his research, even as they questioned his relentlessly negative depiction of his subject. “Here we have Freud the liar, cheat, incestuous child molester, woman hater, money-worshiper, chronic plagiarizer and all-around nasty nut job,” author George Prochnik wrote in the New York Times. “This Freud doesn’t really develop, he just builds a rap sheet.”

Late in life, Dr. Crews turned to a new subject: the case of Jerry Sandusky, the disgraced Penn State assistant football coach who was convicted in 2012 of sexually abusing 10 young boys. Sandusky, who has been imprisoned ever since and continues to insist on his innocence, found a prominent champion in Dr. Crews, who claimed there wasn’t “a shred of credible evidence that he ever molested anyone.”

Dr. Crews wrote a lengthy Medium post in 2021 defending Sandusky and argued, according to an obituary published by his family, that the coach “had been railroaded into prison through a combination of misplaced suspicion, pernicious ‘recovered memory’ theory, and egregious prosecutorial misconduct.”

The younger of two children, Frederick Campbell Crews was born in Philadelphia on Feb. 20, 1933. His father was a patent lawyer, his mother a homemaker.

After graduating from Germantown Academy day school, where he was co-captain of the tennis team, Dr. Crews studied English at Yale University, receiving a bachelor’s degree in 1955. His senior thesis, on Henry James’s late novels, was adapted into his first book, “The Tragedy of Manners”; his second book, a study of author E.M. Forster, was adapted from his dissertation, which he completed en route to earning a PhD in English from Princeton University in 1958.

That same year, he joined the English faculty at Berkeley, where he taught until retiring in 1994 as chair of the department. He co-chaired the Faculty Peace Committee during the Vietnam War and won the school’s Distinguished Teaching Award, in addition to receiving a Guggenheim fellowship for his literary criticism. In 1991, he was elected a fellow of the American Academy of Arts & Sciences.

Survivors include his wife of 64 years, the former Elizabeth “Betty” Peterson; two daughters, Gretchen Detre and Ingrid Crews; a sister; four grandchildren; and a great-granddaughter.

Outside of the classroom, Dr. Crews skied, swam, bodysurfed, hiked and ran, competing in road races until he was 72 and riding his motorcycle for another 15 years. “I ride for one reason only, to find parking spaces in Berkeley,” he explained. “But it’s also a source of amusement, because, with my helmet on, I’m completely invisible to my academic colleagues. There is something very satisfying about that.”