Mailbox may refer to:
- Letter box (also known as a letter plate, letter hole, deed or mail slot), a private receptacle for incoming mail
- Post box (also known as a drop box), a public receptacle for outgoing mail
- Pillar box, a freestanding post box in the United Kingdom and the Commonwealth
- Email box, a destination for electronic messages
- Mailbox (application), email management software for mobile devices
- Mailbox Birmingham, a retail complex in Birmingham, England
- The Mailbox (film), a short movie by the Church of Jesus Christ of Latter-day Saints
- Message queue, a means of interprocess communication in software engineering
- Pigeon-hole messagebox, also known as a cubbyhole, pigeon-hole or pidge
- a square-centric method of addressing a game board in game playing computer automatons; see Board representation (computer chess)