Aleksei Leonov, the Russian cosmonaut who became the first person to walk in space, a thrilling feat that nearly cost him his life but raised Soviet prestige during the Cold War space race against the United States died on Friday in Moscow. He was 85.

His death was announced by Roscosmos, the Russian space agency, on its website.

The milestone achievement by Mr. Leonov, a major in the Soviet Air Force at the time, showed that men could survive in space outside the confines of their craft and presumably walk on the moon one day.

His spacewalk, in March 1965, was seen by television viewers in the Soviet Union and Europe on videotape. Later in the mission, a live telecast showed Mr. Leonov and a fellow cosmonaut strapped in their seats in the cabin.

The spacewalk enabled the Russians once again to upstage the United States in space; they had launched the first satellite, Sputnik, in October 1957 and the first manned spaceflight into orbit, with Yuri Gagarin, in April 1961.

Edward H. White II of the United States Air Force carried out America’s first spacewalk some two and half months later, leaving his two-man Gemini 4 capsule for 20 minutes.

NASA said in a statement that Mr. Leonov’s “venture into the vacuum of space began the history of extravehicular activity that makes today’s Space Station maintenance possible.”

Mr. Leonov would have likely been the first Russian to walk on the moon had the Soviet Union not given up on its lunar ambitions. In 1975, he took part in a pioneering linkup in orbit of Soviet and American spaceships that ultimately led to creation of the International Space Station.

He emerged from his two-man Voskhod 2 for his spacewalk on March 18, 1965, while the spacecraft was orbiting above Earth at some 18,000 miles an hour. He spent about 10 minutes maneuvering, tethered to it with a cord.

“As far as I can remember, I was concentrating fully, cold blooded and relatively unexcited,” Mr. Leonov wrote in a first-person account in Life magazine two months later. “The sight was spectacular! The stars do not blink. The sun seems welded into the black velvet of the sky. The earth alone speeds along.”

What Mr. Leonov did not reveal until many years later was that he and his fellow cosmonaut, Pavel I. Belyayev, who was also an Air Force pilot, were fortunate to have survived.

Mr. Leonov’s specially designed suit had unexpectedly inflated during his walk, and its bulk was preventing him from getting back inside the Voskhod.

“I knew I could not afford to panic, but time was running out,” he recalled in the book “Two Sides of the Moon” (2004), written with the astronaut David Scott, about their experiences in space.

Mr. Leonov slowly deflated the suit by releasing oxygen from it, a procedure that threatened to leave him without life support. But with the reduced bulk, he finally made it inside.

“I was drenched with sweat, my heart racing,” he remembered.

But that, he added, “was just the start of dire emergencies which almost cost us our lives.”

The oxygen pressure in the spacecraft rose to a dangerous level, introducing the prospect that a spark in the electrical system could set off a disastrous explosion or fire.

It returned to a tolerable level, but the cosmonauts never figured out the reason for the surge.

When it came time for the return to Earth, the spacecraft’s automatic rocket-firing system did not work, forcing the cosmonauts to conduct imprecise manual maneuvers during the descent that left them in deep snow and freezing temperatures in a remote Russian forest, far from their intended landing point.

It took several hours for a search party to find them and drop supplies from a helicopter, and they spent two nights in the forest, the first one inside their spacecraft and the second one in a small log cabin built by a ground rescue crew, until rescuers arrived on skis. They then took a 12-mile ski trek to a clearing, where a helicopter evacuated them.

Nearly four years after his spacewalk, Mr. Leonov had another brush with death.

In January 1969, a car in which he was riding with three other former cosmonauts — part of a motorcade that included the Soviet leader Leonid I. Brezhnev — was entering the Kremlin for a celebration marking the docking of two Russian spaceships when a man wielding a pistol in each hand opened fire. The car carrying Mr. Leonov was hit by 14 bullets, which shattered the windows and killed the driver.

“I looked down and saw two bullet holes on each side of my coat where the bullets passed through,” Mr. Leonov told The New York Times Magazine in 1994. “A fifth bullet passed so close to my face, I could feel it going by. When it was over, Brezhnev took me inside and told me, ‘Those bullets were not meant for you, Aleksei, they were meant for me, and for that, I apologize.’”

The gunman had apparently fired on Mr. Leonov’s car thinking Brezhnev was inside, but his car had already peeled off from the motorcade. He was quickly captured, declared insane and sentenced to a mental institution.

In July 1975, Mr. Leonov, flying with Valery N. Kubasov, took part in the good-will mission in which his Soyuz 19 spacecraft docked in orbit with an American Apollo spaceship carrying three astronauts. The cosmonauts and the astronauts exchanged gifts and spent nearly 50 hours together, conducting scientific experiments.

Mr. Leonov, an accomplished amateur artist, presented the astronauts — Thomas P. Stafford, Vance D. Brand and Deke Slayton — with sketches he had drawn of them during joint training.

The cosmonauts were later greeted by President Gerald R. Ford on a visit to the White House and the American spacemen toured the Soviet Union as guests of the cosmonauts.

Aleksei Arkhipovich Leonov was born on May 30, 1934, in the Siberian village of Listvyanka, one of 12 children. His father, Arkhip, a former coal miner who had become a farmer, was sent to a Soviet prison when Aleksei was 3, having been falsely denounced as an enemy of the state, but was released after several years.

When Aleksei was 6, he met a Soviet pilot and became enthralled by aviation. He was admitted to flight-training school, joined the Air Force, flew jet fighters and served as a test pilot. He was among the first group selected for cosmonaut training, in 1960.

He later became director of the cosmonaut corps and retired from the Soviet space program in 1992 as a major general.

Mr. Leonov lived near Moscow, had business interests and spoke around the world on space travel.

Mr. Leonov is survived by his wife, Svetlana, who edited publications issued by Russia’s Cosmonaut Training Center; their daughter, Oksana; and two grandchildren. His daughter Viktoria died before him.

In 1969, Mr. Leonov was sitting in front of a television when Neil Armstrong and Buzz Aldrin became the first moonwalkers as part of the Apollo 11 flight. Though he knew he would never fulfill his dream of walking on the moon, he saw a larger picture that day.

“Everyone forgot, for a few moments, that we were all citizens of different countries on Earth,” he wrote in “Two Sides of the Moon.” “That moment really united the human race.”