Suzanne Massie, who was neither an academic Russia expert nor a diplomat, but who in some 20 visits to the White House in the 1980s coached President Ronald Reagan ahead of his high-wire summitry with the Soviet leader Mikhail S. Gorbachev, died on Sunday in Harrodsburg, Ky. She was 94.

Her death, in hospice care, was confirmed by her family. She had recently moved from her longtime home in Blue Hill, Maine, to an assisted living community in Danville, Ky. to be near a daughter.

An American-born author of books about Russian culture who spoke the language, Ms. Massie held a romantic view of what she called the Russian “soul,” and she formed a bond with a president who liked to understand and communicate complex issues through anecdotes about average people.

At their first meeting, in January 1984, Mr. Reagan was captivated by the lively Ms. Massie, who told Russian jokes and spoke of the spiritualism of the long-suffering Russian people.

“How much do they believe in communism over there?” Mr. Reagan asked her, according to the historian Michael R. Beschloss in his book “Presidential Courage” (2007), a series of portraits of U.S. presidents.

Their scheduled five-minute meeting in the Oval Office ran to nearly an hour. And Mr. Reagan invited her back, again and again.

She became “Reagan’s window on the Soviet Union,” the historian James Mann wrote in “The Rebellion of Ronald Reagan” (2009), a study of his role in ending the Cold War. “She described the country and the Russian people to the president in terms that he understood and found useful.”

It was Ms. Massie who taught Mr. Reagan the Russian proverb “Doveryai no proveryai” (“Trust but verify”), which he uttered to Mr. Gorbachev when they met in Reykjavik, Iceland, in October 1986 — and repeated so often that Mr. Gorbachev grumbled about it.

Before Mr. Reagan’s first meeting with the Soviet leader the prior year in Geneva, he had read Ms. Massie’s “Land of the Firebird: The Beauty of Old Russia,” an admiring history of art and culture in the pre-Bolshevik era published in 1980. “I’m really enjoying it,” he wrote her in a letter, “and it has also helped for the forthcoming meeting.”

Ms. Massie told The New York Times in 1985 that Mr. Reagan was interested in getting beyond “the tight little circle” of Soviet experts who normally had his ear.

“He has not been to the Soviet Union,” she said. “He doesn’t know about the people at all. He’s in the same position as other Americans, despite all his advisers.”

Although Ms. Massie corresponded with Mr. Reagan and met with him before and after trips she made to Moscow — including a private lunch on the Oval Office patio with the president and the first lady, Nancy Reagan — memoirs by Reagan officials involved in U.S.-Soviet relations portray her as a minor figure.

But Mr. Mann wrote that she “played a more significant role” than is generally known. She served as an unofficial emissary, carrying messages between Mr. Reagan and Moscow, and she humanized Russians for Mr. Reagan at a time when he was revising his view of the Soviet Union as an “evil empire” and reaching out to Mr. Gorbachev to ease nuclear tensions.

Ms. Massie painted Mr. Gorbachev as a genuine reformer battling Kremlin hard-liners. It was an assessment that Mr. Reagan came to agree with, over the objections of Cold War hawks in and outside government, who saw Mr. Gorbachev as just another Soviet strongman.

According to historians, Ms. Massie didn’t lead the president to his softer line. But she was an unconventional voice confirming his instincts, which ultimately led to the 1987 treaty limiting some nuclear missiles and to Mr. Reagan’s effectively declaring the end of the Cold War in Moscow in 1988.

Suzanne Liselotte Marguerite Rohrbach was born in Queens on Jan. 8, 1931, the eldest of three daughters of Suzanne (Nobbs) Rohrbach and Maurice J. Rohrbach, a Swiss diplomat. She grew up in Philadelphia, where her father was the Swiss consul general.

She graduated from Vassar College in 1952 and two years later married Robert K. Massie, who was a magazine writer at the time.

The couple’s first child, Robert, had hemophilia. Caring for him, which the Massies described in a searing memoir, “Journey” (1975), turned out to be an unlikely portal into Russian culture and, ultimately, the Oval Office.

The Massies learned that Czar Nicholas II and his wife, Alexandra, the last of the Romanovs, had a son with hemophilia. Mr. Massie went on to write a best-selling history, “Nicholas and Alexandra” (1967), with Ms. Massie serving as editor and researcher. Seeking some respite from raising a disabled child, she took Russian lessons.

“To keep my mind intact, to keep from turning around in my cage like a panic-stricken animal,” she later wrote, “I had to do something hard, something mentally challenging.”

She made eight visits to Russia between 1967 and 1972. She also cultivated ties with U.S. senators interested in the Soviet Union. And she wrote “Land of the Firebird,” which the exiled Russian author Alexander I. Solzhenitsyn praised for furthering a “true understanding of Russia among Americans.”

Reviewing the book for The New York Times, John Leonard was less admiring. He dismissed it as simplistic and overcooked at the same time, “a sort of heavy breathing comic strip.”

Ms. Massie’s first marriage ended in divorce in 1990. Two years later, she married Seymour Papert, a prominent computer theorist, who died in 2016.

She is survived by a sister, Simone Dur; three children, Robert K. Massie IV, Susanna Massie Thomas and Elizabeth Massie; seven grandchildren; and three great-grandchildren.

Ms. Massie was a fellow of the Harvard Russian Research Center (now the Davis Center for Russian and Eurasian Studies) from 1985 to 1997. Her other books include “Trust but Verify: Reagan, Russia and Me” (2013).

Ms. Massie served as a back-channel messenger between Mr. Reagan and an official in Moscow, Radomir Bogdanov, the deputy director of the Institute for U.S. and Canadian Studies, a Russian think tank.

Mr. Bogdanov was also a known K.G.B. agent; both Ms. Massie and Mr. Reagan believed he was a conduit for unofficial diplomacy with Mr. Gorbachev.

But Ms. Massie ultimately overplayed her hand at the White House. In 1987, she asked Mr. Reagan to name her to replace the departing ambassador to Russia. But the president had already settled on his choice: Jack F. Matlock Jr., a Soviet expert on the National Security Council.

White House officials moved to limit Ms. Massie’s access to the Oval Office. Some were skeptical that the messages she brought from Moscow really came from Mr. Gorbachev. A new national security adviser, Frank Carlucci, insisted on sitting in on meetings between Ms. Massie and the president.

Mr. Carlucci attended one on Feb. 25, 1987. He came away reassured that she had no ulterior agenda and was not — as some security officials speculated — a dupe being used by Moscow to manipulate the president.

“I wanted to make sure,” Mr. Carlucci told Mr. Mann in 2005 for his book. “They had a wonderful relationship, and at the end of the meetings, she would give him a kiss on the cheek. She was perfectly harmless.”