The Youth International Math Olympiad (YIMO) is a free online mathematics competition open worldwide. The official site names NXT Horizon and STEMise as its organizers. YIMO II, held in August 2026, has concluded. Its published format had Beginner and Advanced divisions, 20 integer-answer problems and the top 10 per division progressing to a computational/proof-style final.
Official co-organizer STEMise announces YIMO III for December 19–20, 2026, with registration open. Students choose one window: December 19 at 9:30 p.m. EST or December 20 at 11:00 a.m. EST. The form adds an untimed, unproctored Division 3 alongside competitive Beginner and Advanced divisions. Competitive entrants use live camera-on proctoring on a separate device while taking the test in Exam.net. A parent or guardian must confirm permission in the form.
The current form does not state a registration closing date, exact third-edition prize pool or final-round selection threshold. The previous August cutoff and EDT windows are historical; they do not govern December registration.
Checked November 4, 2026 using the official YIMO site and archive, co-organizer’s edition history, STEMise third-edition announcement and linked YIMO III registration form.