Malleus (Latin for "hammer") may refer to:
- Malleus, a bone in the middle ear;
- Malleus (disease), a bacterial infection
- Malleus (mollusc), a genus of bivalves.
- Malleus Maleficarum (Hammer of Witches), an early modern European treatise on witches.
- Malleus Scotorum (Hammer of the Scots), byname of King Edward I of England
- Malleolus, a structure in mammalian skeletal anatomy; etymologically, the diminutive of malleus