The following 22 categories and subcategories are those that will be used at ISEF 2026, Phoenix, Arizona.

National Geographic Society has made a two-year commitment to sponsor the earth and environmental sciences category in addition to a delegation of finalists from Washington, DC. Additionally, National Geographic will be sponsoring the Pin Exchange, a signature event at Regeneron ISEF, featuring an ice breaker activity where students trade lapel pins representing their state or country with as many students as they can meet from other places in the United States and around the world.