A sou'wester is a waterproof hat, traditionally worn by fishermen. It has a wide brim, longer at the back than at the front to prevent rainwater running down the back of the neck. Sou'westers were traditionally made of oilskin, a heavy cotton material waterproofed with oil. Sou'wester is also sometimes the name given to an oilskin coat. Such a coat and hat may be referred to simply as oilskins.
Sou'westers are often bright yellow in colour.