Yabby or Yabbie is a name given in Australia to two different kinds of crustacean.
- A freshwater yabby is a crayfish of the genus Cherax (infraorder Astacidea, family Parastacidae). They are often caught for food. They are frequently found in dams, ponds, lakes and rivers in Australia's Eastern States. They are usually caught by way of a baited string or trap. A widespread species is the common yabby, Cherax destructor.
- A marine yabby is a ghost shrimp (infraorder Thalassinidea), which lives in deep burrows in the intertidal zone. They are used as bait for fishing, especially in Queensland and northern New South Wales. A common species in south-eastern Australia is the Bass yabby, Trypaea australiensis.
The name is derived from the word yabij in an Aboriginal language of the Pama–Nyungan family.