Reliability may refer to:
- Reliability (engineering) and also a branch of statistics, the ability of a system or component to perform its required functions under stated conditions for a specified period of time.
- Reliability (psychometrics), of a set of data and experiments
- High reliability is informally reported in "nines"
- Reliabilism in philosophy and epistemology
- Data reliability, a property of some disk arrays in computer storage
- Reliability theory, as a theoretical concept, to explain biological aging and species longevity
- Reliability (computer networking), a category used to describe protocols
- Reliability (semiconductor), outline of semiconductor device reliability drivers