This timeline documents all of the events of the 2009–10 South-West Indian Ocean cyclone season which is the period that tropical cyclones formed in the Indian Ocean.

The scope of this article is limited to tropical cyclones that form in the Indian Ocean 30°E and 90°E to the south of the equator.

When a zone of disturbed weather form or moves into the South-West Indian Ocean it is assigned a number and monitored by Météo-France who run the Regional Specialized Meteorological Center (RSMC) on Réunion Island.

The United States Joint Typhoon Warning Center (JTWC) also issue warnings on tropical cyclones in this region assigning a number with an "S" suffix.

When monitoring a tropical cyclone the Joint Typhoon Warning Center will assess the cyclones intensity on the Saffir–Simpson hurricane scale whilst RSMC La Réunion, Mauritius and Madagascar use the Southwest Indian Ocean Tropical Cyclone Intensity Scale to assess a tropical cyclones intensity.