The bill is yellow and the legs and webbed feet are orange. The body is grey-brown and the wings have a blue-violet wing patch within thin white bars. The introduced Mallard is a large, dabbling duck with the distinctive males having a glossy green head and neck, a white collar and a chestnut breast. This refers to its classic 'duck' bill, which is adapted for feeding in water, with grooves called lamellae that help to grip vegetation and filter out water.

The specific name for the Mallard - platyrhynchos - means 'flat billed'.