Yellow flag

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
 * The Yellow Flag, 1937 German drama film
 * Yellow Banners of the Eight Banner system
 * Plain Yellow Banner
 * Bordered Yellow Banner