The Roaring Forties is a name given, especially by sailors, to the winds at latitudes between 40°S and 50°S.

So called because of the boisterous and prevailing westerly winds, which are especially strong in the South Indian Ocean.

The winds were probably first identified by Dutch sailor Henderik Brouwer in 1610 as a means to rapidly transit across the Indian Ocean en route to Batavia.