503 (disambiguation)

503 may refer to:

• 503 (number)
• 503, a year
• 503, a track by Hans Zimmer on the Angels & Demons soundtrack
• 503 Service Unavailable, an HTTP status code
• Area code 503, a North American telephone area code in northwestern Oregon
• BMW 503, a luxury car
• Country code +503, for El Salvador
• FN 503, a semi-automatic pistol manufactured by FN Herstal
• A type of jeans, commonly in Levi's and Edwin
• A type of steel used for making bicycle frames