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.

Examples include

• antrum cardiacum - a dilation that occurs in the esophagus near the stomach (forestomach)
• mastoid antrum - Synonym: antrum mastoideum, tympanic antrum, Valsalva's antrum
• pyloric antrum - the initial portion of the pyloric part of the stomach
• antrum follicularum - the cavity in the epithelium that envelops the oocyte