Yellow flag may refer to:
Iris pseudacorus, an aquatic flowering plant A flag of a yellow colour: Yellow flag (contagion), historically displayed on ships to indicate the presence of disease or quarantine (obsolete); also used in some cities to mark a recent death in a neighborhood, regardless of cause Racing flags, used in motor sports to indicate hazardous conditions Penalty flag, used in various sports including American football Yellow Flag Line, transport on the Chao Phraya River, with service indicated by the flag color Yellow Dragon Flag, the flag of the Qing dynasty Yellow Jack (flag), the signal flag that represents the letter Q A political flag used to represent liberalism or capitalism (cf. red flag, black flag) The Yellow Flag, 1937 German drama film Yellow Banners of the Eight Banner system Plain Yellow Banner Bordered Yellow Banner