Inert may refer to:
- Chemically inert, not chemically reactive
- Inert knowledge, information which one can express but not use
- Inert ingredient, a component of the excipient of a pharmaceutical drug
- Inert munition, a round that does not contain any energetic material
- Inert prime, a type of behaviour of a prime under an algebraic extension
- Inert waste, waste which is neither chemically nor biologically reactive and will not decompose