Keystone

Keystone may refer to:

• Keystone (architecture), a central stone or other piece at the apex of an arch or vault
• The keystone effect, caused by projecting an image onto a surface at an angle, or by photography at an angle
• Keystone (cask), a wooden or plastic fitting used in ale casks
• Keystone module, a type of data connector mounted in walls and patch panels
• Keystone species, species that have a larger effect on their environment than is purely due to their abundance
• Operation Keystone during World War II
• The Keystone asterism in the Hercules constellation
• Keystone Press Awards, given to Pennsylvania reporters
• Keystone (limestone), a type of limestone quarried in the Florida Keys
• Keystone, a variety of slotted screwdriver blade
• Keystone Initiative, a medical protocol to reduce infection rates