linguistic:voice_change, quality:corruption
1920–1924 Olympics

Nurmi made his international debut in August at the 1920 Summer Olympics in Antwerp, Belgium. He took his first medal by finishing second to Frenchman Joseph Guillemot in the 5000 m. This would remain the only time that Nurmi lost to a non-Finnish runner in the Olympics. He went on to win gold medals in his other three events: the 10,000 m, sprinting past Guillemot on the final curve and improving his personal best by over a minute, the cross country race, beating Sweden's Eric Backman, and the cross country team event where he helped Heikki Liimatainen and Teodor Koskenniemi defeat the British and Swedish teams. Nurmi's success brought electric lighting and running water for his family in Turku. Nurmi, however, was given a scholarship to study at the Teollisuuskoulu industrial school in Helsinki.

Buoyed by his defeat to Guillemot, Nurmi's races became a series of experiments which he analyzed meticulously. Previously known for his blistering pace on the first few laps, Nurmi started to carry a stopwatch and spread his efforts more uniformly over the distance. He aimed to perfect his technique and tactics to a point where the performances of his rivals would be rendered meaningless. Nurmi set his first world record on the 10,000 m in Stockholm in 1921. In 1922, he broke the world records for the 2000 m, the 3000 m and the 5000 m. A year later, Nurmi added the records for the 1500 m and the mile. His feat of holding the world records for the mile, the 5000 m and the 10,000 m at the same time has not been matched by any other athlete before or since. Nurmi also tested his speed in the 800 m, winning the 1923 Finnish Championships with a new national record. After excelling in mathematics, Nurmi graduated as an engineer in 1923 and returned home to prepare for the upcoming Olympic Games.

Nurmi's trip to the 1924 Summer Olympics was endangered by a knee injury in the spring of 1924, but he recovered and resumed training twice a day. On 19 June, Nurmi tried out the 1924 Olympic schedule at the Eläintarha Stadium in Helsinki by running the 1500 m and the 5000 m inside an hour, setting new world records for both distances. In the 1500 m final at the Olympics in Paris, Nurmi ran the first 800 m almost three seconds faster. His only challenger, Ray Watson of the United States, gave up before the last lap and Nurmi was able to slow down and coast to victory ahead of Willy Schärer, H. B. Stallard and Douglas Lowe, still breaking the Olympic record by three seconds. The 5000 m final started in less than two hours, and Nurmi faced a tough challenge from countryman Ville Ritola, who had already won the 3000 m steeplechase and the 10,000 m. Ritola and Edvin Wide figured that Nurmi must be tired and tried to burn him off by running at world-record pace. Realizing that he was now racing the two men and not the clock, Nurmi tossed his stopwatch onto the grass. The Finns later passed the Swede as his pace faded and continued their duel. On the home straight, Ritola sprinted from the outside but Nurmi increased his pace to keep his rival a metre behind.

In the cross country events, the heat of 45 °C (113 °F), caused all but 15 of the 38 competitors to abandon the race. Eight finishers were taken away on stretchers. One athlete began to run in tiny circles after reaching the stadium, until setting off into the stands and knocking himself unconscious. Early leader Wide was among those who blacked out along the course, and was incorrectly reported to have died at the hospital. Nurmi exhibited only slight signs of exhaustion after beating Ritola to the win by nearly a minute and a half. As Finland looked to have lost the team medal, the disoriented Liimatainen staggered into the stadium, but was barely moving forward. An athlete ahead of him fainted 50 metres from the finish, and Liimatainen stopped and tried to find his way off the track, thinking he had reached the finish line. After having ignored shouts and kept the spectators in suspense for a while, he turned into the right direction, realised his situation and reached the finish in 12th place and secured team gold. Those present at the stadium were shocked by what they had witnessed, and Olympic officials decided to ban cross country running from future Games.

In the 3000 m team race on the next day, Nurmi and Ritola again finished first and second, and Elias Katz secured the gold medal for the Finnish team by finishing fifth. Nurmi had won five gold medals in five events, but he left the Games embittered as the Finnish officials had allocated races between their star runners and prevented him from defending his title in the 10,000 m, the distance that was dearest to him. After returning to Finland, Nurmi set a 10,000 m world record that would last for almost 13 years. As of July 2024, this is the second-longest-standing world record for the men's 10,000 metres. Kenenia Bekele's world record set in August 2005 in Brussels stood for over 15 years. Nurmi now held the 1500 metres, the mile, the 3,000 metres, the 5,000 metres and the 10,000 metres world records simultaneously.