B1, B.I, B.1 or B-1 may refer to:

• Bradykinin receptor B1, a human protein
• Cinnamtannin B1, a condensed tannin found in cinnamon
• Combretastatin B-1, a stilbenoid found in Combretum sp.
• Fumonisin B1, a toxins produced by several species of Fusarium molds
• B-1 cell, a lymphocyte type
• Arecatannin B1, a tannin found in the betel nut
• Proanthocyanidin B1, a B type proanthocyanidin
• Vitamin B₁, also known as thiamine

• B1 TV, a Romanian TV channel
• A class of FM radio broadcasting in North America

• Rockwell B-1 Lancer, a United States Air Force strategic bomber
• B1 (New York City bus) serving Brooklyn
• B1 type submarine, a World War II Imperial Japanese Navy submarine class
• Alsace-Lorraine B 1, an Alsace-Lorraine P 1 class steam locomotive
• Marussia B1, a high-performance luxury sports coupé built by Russian automaker Marussia Motors
• GS&WR Class B1, a Great Southern and Western Railway Irish steam locomotive
• HMS B1, a B-class submarine of the Royal Navy
• LB&SCR B1 class, an 1882 British express passenger steam locomotive
• GCR Class 8C, classified B1 during LNER ownership, reclassified B18 in 1943
• LNER Thompson Class B1, a British steam locomotive class
• NER Class B1, a class of British steam locomotives
• NCC Class B1, a Northern Counties Committee Irish steam locomotive
• Pennsylvania Railroad class B1, an American electric locomotive
• Saturn B-1, a 1959 four-stage rocket
• USS B-1, a United States Navy B-class submarine
• Brasilsat B1, a 1994 communication satellite
• Char B1, a French heavy tank
• B1 Centauro, an Italian wheeled tank destroyer
• Boom XB-1 Baby Boom, an American technology demonstrator aircraft
• Finnish Steam Locomotive Class B1

• B1 (file format)
• B1 (classification), a medical-based Paralympic classification for blind sport
• B-1/B-2 Visa, issued by the United States to a foreign citizen seeking to enter the United States of America for business purposes
• A subclass of B-class stars
• B1, an international standard paper size (707 × 1000 mm), defined in ISO 216
• A level in the Common European Framework of Reference for Languages
• A security class in the TCSEC
• the code for permission to use specific land or premises for offices, light industry in town and country planning in the United Kingdom
• A sentient banana in the children's TV series Bananas in Pyjamas
• B1, a model of battle droid in the Star Wars franchise
• B1, Sydney Australia B-Line bus route
• Chopin's Ballade No. 1
• The darkest sky on the Bortle scale

• All pages with titles beginning with B1
• All pages with titles containing B1
• B01 (disambiguation)
• BI (disambiguation)
• 1B (disambiguation)