Barrier

Barrier may refer to:

• Breakwater, a barrier on a coast to protect a harbour from ocean currents and waves
• Defensive wall, built to protect against an attack
• Blood–brain barrier, a separation of circulating blood and the brain extracellular fluid
• Barrier reef, a type of coral reef running along a coast
  • Belize Barrier Reef, off the coast of Belize
  • Great Barrier Reef, off the coast of Queensland in north-east Australia
• Dam