Blue flag

Blue flag or Blue Flag may refer to:
 * Sport and recreation
 * Blue Flag beach, a beach or marina that meets certain quality standards
 * Blue Flag, the flag of Chelsea F.C.
 * Blue flag, a particular Flag
 * Blue flag, a particular Racing flags
 * Botany
 * Larger Blue Flag or Iris versicolor, a type of iris
 * Slender Blue Flag or Iris prismatica, a type of iris
 * Transport
 * Blue flag, a particular Flag in railway use.
 * Blue sign used by European waterways vessels passing on the starboard side
 * Military
 * Blue Flag (Israeli Air Force exercise), the name of an Israeli Air Force exercise
 * Blue Flag (United States Air Force exercise), the name of a United States Air Force command and control exercise
 * Other
 * Blue Flag (manga), a manga series by KAITO.
 * "The Blue Flag", World War I song composed by Carrie Jacobs-Bond
 * Blue Flag, common representation of the street gang Crips