Cyclone Tracy was a tropical cyclone that devastated the city of Darwin, Northern Territory, Australia, from 24 to 26 December 1974. The small, developing easterly storm had been observed passing clear of the city initially, but then turned towards it early on 24 December. After 10:00 p.m. ACST, damage became severe, and wind gusts reached 217 kilometres per hour (134.84 mph) before instruments failed. The anemometer in Darwin Airport control tower had its needle bent in half by the strength of the gusts.

Residents of Darwin were celebrating Christmas, and did not immediately acknowledge the emergency, partly because they had been alerted to an earlier cyclone (Selma) that passed west of the city, and did not impact it in any way. Additionally, news outlets had only a skeleton crew on duty over the holiday.

Tracy killed 71 people, caused A$837 million in damage (1974 dollars), or approximately A$7.2 billion (2022 dollars), or US$5.2 billion (2022 dollars). It destroyed more than 70 percent of Darwin's buildings, including 80 percent of houses. It left more than 25,000 out of the 47,000 inhabitants of the city homeless prior to landfall and required the evacuation of over 30,000 people, of whom many never returned. After the storm passed, the city was rebuilt using more stringent standards "to cyclone code". The storm was the second-smallest tropical cyclone on record (in terms of gale-force wind diameter), behind only Tropical Storm Marco in 2008.