A seal is a device or material that helps join systems, mechanisms or other materials together by preventing leakage (e.g. in a pumping system), containing pressure, or excluding contamination. The effectiveness of a seal is dependent on adhesion in the case of sealants and compression in the case of gaskets. Seals are installed in pumps in a wide range of industries including chemicals, water supply, paper production, food processing and many other applications.

A stationary seal may also be referred to as a 'packing'.

Seal types: