The International Junior Science Olympiad (IJSO) is an annual in-person competition in the natural sciences — physics, chemistry, and biology — for students under the age of 16. It brings together national teams of young scientists from countries around the world to solve theoretical and experimental problems, with the goal of promoting scientific excellence and fostering international friendships among junior students.
The competition rotates host countries each year. The 2026 edition is held in Sofia, Bulgaria. Each participating country sends a team selected through its own national junior science competition. Students cannot apply individually; they must qualify through their country's national selection process.
The official July 30, 2026 registration announcement addresses national coordinators and delegations. It describes 57 pre-registered countries and an estimated capacity of 40, and says registration does not guarantee placement. No universal student fee or coverage package was confirmed; the prior blanket claim that participation is free has been removed.
Checked November 3, 2026: the official 2026 host page, preliminary program, and registration guidelines confirm Sofia, December 2-9, and the August 1-31 delegation registration window. These official documents were retrieved directly when web extraction failed. The main IJSO page confirms the under-16-on-December-31 age rule. Exact participating-country eligibility, national selection cutoffs, and fees remain unverified; no unrestricted worldwide entry is asserted.