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