Blue flag
Blue flag stands for:
- Blue flag (quality mark) , quality mark on beaches and ports
- Blue flag , flag symbols in motorsport, see list of flag symbols in motorsport # Blue flag
- Blauer Peter , from the flag alphabet, letter P , which announces the departure of the (sailing) ship in 24 hours
- blue flag , from the flag alphabet, checkered flag at a regatta
- blue board , identification of the encounter in inland navigation in left-hand traffic, see Rhine navigation # traffic rules and ascent of an inland waterway vessel