TOKYO—The Tokyo 2020 Olympics were postponed until 2021 on Tuesday as the coronavirus pandemic spreads world-wide, an unprecedented shifting of the world’s largest sporting event that casts a universe of athletes, broadcasters, sponsors and sports organizations into a period of protracted uncertainty.

Japanese Prime Minister Shinzo Abe and IOC President Thomas Bach agreed in a phone call Tuesday to delay the Games, previously scheduled to start July 24, for around one year. No new date was set, and the postponement throws...