🇨🇳 Deng Leyan

The International Mathematical Olympiad has run since 1959 and is the oldest of the international science olympiads. Its format has barely changed: each contestant sits alone for two consecutive days, four and a half hours per day, three problems per paper. The problems are drawn from algebra, combinatorics, geometry and number theory, and they require no calculus and no university machinery — which is precisely what makes them hard. Everything needed to solve them is taught in secondary school. What is not taught is the idea, and the idea is the entire examination.

A perfect score means six complete, rigorous, correctly written proofs. Coordinators from the host country read every script twice, alongside the leader and deputy leader of the contestant's own delegation, and a proof that reaches the right answer by an argument with a gap does not score seven. Contestants who are strong enough to be in the room at all typically lose points not through ignorance but through a case they did not check or a bound they did not justify. This is why perfect scores are rare even among gold medallists: in most years fewer than ten of several hundred contestants achieve one, and in some years nobody does.

The 67th edition was itself a first. It ran from 10 to 21 July 2026 and was hosted by Shanghai High School — the first time in the competition's history that a secondary school, rather than a university or a national body, had staged the IMO. Participation set records for both the number of countries, 117, and the number of contestants, 666. Deng took the contestants' oath at the opening ceremony on 14 July alongside the Swiss contestant Hongjia Meng, an appointment that goes to a student the host delegation puts forward publicly.

China won the team competition with 232 points, twenty-five clear of the United States, its twenty-sixth team title. All six Chinese contestants took gold; the delegation collected no silver and no bronze. Two of Deng's teammates also scored 42/42 — Zhang Bailing of Shanghai High School and Liu Che of the Second High School Attached to East China Normal University — so three of the seven perfect scores in the world that year came from a single team. Deng became the fifth Chinese contestant ever to score perfectly twice, after Luo Wei, Fu Yunhao, Wei Dongyi and Shi Haojia.

His record before Shanghai was already unusual. In the eighth grade he won the Weiming Award at Peking University's mathematics summer camp. On 3 November 2024 he placed fifth in the world in the combinatorics and probability track of the Alibaba Global Mathematics Competition — an open contest with a largely postgraduate and professional field — and was reported as the first pre-university student to medal in that event. In December 2024 he took first place with a perfect score at the 40th Chinese Mathematical Olympiad, the national selection contest that feeds the IMO team.

At the 2025 IMO in Queensland, Australia, it was Terence Tao — the Australian-American mathematician who won IMO gold at thirteen and the Fields Medal at thirty-one, and whom Deng has named as his idol — who placed the gold medal around his neck. Deng has spoken publicly about being an ordinary student in subjects other than mathematics. Speaking at a school opening ceremony in August 2025, he said flatly that no amount of study would produce a top English mark for him. He has since secured guaranteed university admission with his choice of major, and passed over computer science for mathematics.