B1

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

Biology and chemistry

Rockwell B-1 Lancer, a United States Air Force strategic bomber
B1-class Melbourne tram
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
Ceylon Government Railway B1, a steam locomotive class
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
Spanish submarine B-1, a Spanish Navy submarine
USS B-1 (SS-10), 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
Barnard 1
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
B-Line (Sydney) bus route, numbered B1, Australia
BRT Sunway Line, numbered B1 on maps, Malaysia
Chopin's Ballade No. 1
The darkest sky on the Bortle scale
Line B1 (Tianjin Metro), China
Unitree B1, a robot dog made by Unitree Robotics