In biology, antrum is a general term for a cavity or chamber, which may have specific meaning in reference to certain organs or sites in the body.
In vertebrates, it may refer specifically to:
- Antrum follicularum, the cavity in the epithelium that envelops the oocyte
- Mastoid antrum, a cavity between the middle ear and temporal bone in the skull
- Stomach antrum, either
- Maxillary antrum or antrum of Highmore, the maxillary sinus, a cavity in the maxilla and the largest of the paranasal sinuses
In invertebrates, it may refer specifically to:
- Antrum of female lepidoptera genitalia