Diaphragm may refer to:

• Thoracic diaphragm, a thin sheet of muscle between the thorax and the abdomen
• Pelvic diaphragm or pelvic floor, a pelvic structure
• Urogenital diaphragm or triangular ligament, a pelvic structure

• Diaphragm (optics), a stop in the light path of a lens, having an aperture that regulates the amount of light that passes
• Diaphragm (acoustics), a thin, semi-rigid membrane that vibrates to produce or transmit sound waves
• Diaphragm (birth control), a small rubber dome placed in the vagina to wall off the cervix, thus preventing sperm from entering
• Diaphragm (mechanical device), a sheet of a semi-flexible material anchored at its periphery
• Diaphragm (structural system), a structural engineering system used to resist lateral loads

• Diaphragm arch
• Diaphragm pump
• Diaphragm seal, a membrane that seals an enclosure
• Diaphragm shutter, a type of leaf shutter consisting of a number of thin blades in a camera
• Diaphragm valve
• Diaphragm wall
• Diaphragma, a genus of algae
• Lamina (disambiguation)
• Membrane (disambiguation)