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)
  • Racing flags used in motor sports to indicate hazardous conditions
  • Penalty flag used in various sports including American football
• Green-Yellow Flag Line transport on the Chao Phraya River north of Bangkok