Subject may refer to:

In knowledge and education

• An area of knowledge, a topic, an area of interest or study
• Course (education), a unit of academic instruction
  • List of academic disciplines
• Subject (grammar), one of two main constituent parts of a sentence
  • Subject case or nominative case, the grammatical case for a noun
• Subject term or index term, in information retrieval, a descriptor of a document used in bibliographic records
• Research subject, an organism (human or otherwise) that is observed for purposes of research

In philosophy

• Subject (philosophy), a being which has subjective experiences, subjective consciousness or a relationship with another entity
• Subject-object problem, the issue of how actors or observers relate to things which are observed or acted upon
• Subject-object based metaphysics, author Robert M. Pirsig's term for the dominant view of metaphysics in Western philosophy
• Subject-SUBJECT consciousness, a concept proposed by Harry Hay to describe non-heterosexual relationship dynamics
• Hypokeimenon or subiectum, in metaphysics, the essential being of a thing