The 1999-00 Australian region cyclone season was an event in the annual cycle of tropical cyclone formation and ran from November 1, 1999 to April 30, 2000. The regional tropical cyclone operational plan also defines a "tropical cyclone year" separately from a "tropical cyclone season", with the "tropical cyclone year" for this season lasting from July 1, 1999 to June 30, 2000.