Subject (Latin: subiectus "lying beneath") may refer to:
- Subject (documents) (subject classification; subject indexing; subject searching)
- Subject term or index term, descriptor of a document used in bibliographic records
- Subject (philosophy), a being that has subjective experiences, subjective consciousness, or a relationship with another entity
- Subject–object problem, the issue of how actors or observers relate to things that are observed or acted upon
- Subjects (programming), core elements in the subject-oriented programming paradigm
- The melodic material presented first in a fugue
- Either of the two main groups of themes (first subject, second subject) in sonata form
A subject is an individual subjected to the rule by an elite, see feudalism
- subjects in medieval feudalism, see commoners
- subjects in modern constitutional monarchies, such as the United Kingdom, see British subject
- A subject is someone or something that undergoes testing in a scientific experiment.