CD3 or CD-3 may be:
- CD3 (immunology), an antigen, cluster of differentiation protein (immunology), part of the T cell receptor (TCR) complex on a mature T lymphocyte
- Ford CD3 platform
- MediaMax CD-3, copy protection scheme
- MiniCD, a 3-inch CD
- 3-inch CD single
- Color Developing Agent 3, the color developer for E-6 process