B13 may refer to:

• 130 mm/50 B13 Pattern 1936, Soviet naval gun
• B13 (New York City bus) serving Brooklyn
• B13tech, a futuristic fictional technology created by the character Brainiac 13
• Bensen B-13, a Bensen aircraft
• Boston Thirteens, a Rugby League club competing in the USARL
• District B13, a movie featuring David Belle
• HLA-B13, an HLA-B serotype
• Martin XB-13, a version of the Martin B-10 bomber
• Caro–Kann Defence, Exchange Variation (ECO code: B13), an opening in the game of chess
• Moseley, a suburb of Birmingham, England, from its postcode
• Orotic acid, formerly known as Vitamin B₁₃
• Boron-13 (B-13 or ¹³B), an isotope of boron
• A chassis of the Nissan Sentra
• Queensland B13 class locomotive
• 13 amp, type B – a standard circuit breaker current rating
• Jalan Uniten–Dengkil, in Selangor, Malaysia
• LNER Class B13, a class of British steam locomotives
• Block 13, Kuwaiti TV Series

• 13B (disambiguation)