B2 or B-2 may refer to

• Vitamin B2.
• B-2 Spirit, a United States Air Force stealth bomber.
• B2, the IATA code for Belavia.
• HMS B2 , a B-class submarine of the Royal Navy.
• USS B-2, a B-class submarine of the United States Navy.
• B2, an international standard paper size (707×1000 mm), defined in ISO 216.