B6 or B-6 may refer to:

• Vitamin B6, Pyridoxine.
• B6, a Mazda piston engine.
• B6, the IATA code for JetBlue Airways.
• The Keystone B-6, a biplane bomber of the United States Army Air Corps.
• HMS B6 , a B-class submarine of the Royal Navy.
• B6, an international standard paper size (125×176 mm), defined in ISO 216.