Her husband, Antonio F. Weiss, said the cause was cancer.
Hunnewell joined the magazine as an editorial intern in the late-1980s, when it was run out of an 8-by-14-foot office in the Upper East Side brownstone of its co-founder and editor George Plimpton.
She remained associated with the magazine for the next 30 years, including a transformative and sometimes turbulent period after Plimpton’s death at 76 in 2003.
During that time the magazine redesigned its pages, broadened its scope and, in 2018, installed a woman as its top editor, after one of Plimpton’s male successors resigned amid accusations of sexual misconduct toward female employees and writers.
Hunnewell, who had earlier been Paris editor of the magazine, was named publisher in 2015, taking over from Weiss, an investment banker who had joined the government as a counselor to Treasury Secretary Jack Lew in the Obama administration.
Novelist Mona Simpson, a member of The Paris Review board, recalled Hunnewell as the most hands-on publisher the magazine had ever had. “She really cared about the possibilities of a literary magazine,” Simpson said.
In late 2017, after its editor, Lorin Stein, resigned over the misconduct allegations, Hunnewell successfully championed hiring Emily Nemens to replace him, even though, as a co-editor of The Southern Review, she was far outside The Paris Review’s clubby literary circle.
In announcing Nemens’ hiring, Hunnewell cited her “proven track record for finding diverse new voices outside established networks.”
Simpson said Hunnewell had notably managed to unify the magazine’s different constituencies.
“The Paris Review is known for its hysterically extensive masthead,” she said, “and Susannah was the only person in the world who could coax all these founders, editors, associates, readers, contributors and board members not only to get along but to have wild fun together.”
Terry McDonell, a former editor of Esquire and a former president of The Paris Review’s board, called Hunnewell a protector of the essential DNA of the magazine, which Plimpton helped start in Paris in 1953 and whose modest circulation had belied its influence in the literary world as a showcase for writers and a discoverer of new talent.
“She just had this wonderful enthusiasm not just for literature, but for the life around it,” McDonnell said of Hunnewell. “She represented a really optimistic kind of continuity.”
Susannah Gordon Hunnewell was born in Boston on July 16, 1966. Her father, Francis Oakes Hunnewell, was an international investment banker and an entrepreneur and a descendant of the family on whose land the town of Wellesley, Massachusetts, was founded. He died in 2010. Her mother, Elizabeth Milton Hunnewell, is a freelance writer.
The family moved to Paris shortly after Susannah was born, and she attended the Ecole Active Bilingue, a school that teaches in French and English. The family returned to Wellesley when she was 15, and she attended the Winsor School for young women in Boston and then Harvard, from which she graduated with a degree in English.
As a young editorial assistant at The Paris Review, Hunnewell read through submissions relegated to the slush pile and edited short stories and articles for print. She was also among the staff members who Plimpton credited with helping him put together “The Paris Review Anthology” (1990).
It was at The Review that she met Weiss, who was an editor of the magazine and Plimpton’s assistant at the time.
After leaving The Review, Hunnewell worked at The New York Times as a news clerk. She went on to be an editor at the newly created American edition of Marie Claire magazine and then associate editor at George, the political magazine founded by John F. Kennedy Jr. All the while she maintained her ties to The Paris Review.
She and Weiss moved to Paris in 2000 after he had entered investment banking and had become a partner at the investment bank Lazard, focusing on Europe.
As Paris editor, Hunnewell (as she continued to be known professionally, though she took her husband’s surname) contributed to the magazine’s tradition of publishing extended interviews with famous authors, talking with subjects like Harry Matthews, Kazuo Ishiguro, Michel Houellebecq and Emmanuel Carrère.
Last year, in a ceremony in New York, she was named a chevalier in the French order of arts and letters.
In addition to her mother and husband, now a senior fellow at the John F. Kennedy School of Government at Harvard, Hunnewell is survived by three sons, Niccolò, Ottocaro and Cosimo; a brother, Oakes; and a sister, Lee.