B103 may refer to:
B103 (New York City bus), bus route in the New York City borough of Brooklyn Bacillus virus B103, a genus of the virus species Picovirinae St. Jerome beside a pollard willow, etching B103 on the list of etchings by Rembrandt B103, a locomotive in the British CIE 101 Class
Radio stations KBWS-FM (102.9 FM, "Superstar Country B103"), in the Sisseton, South Dakota, area WZKR (103.3 FM, formerly broadcast a country format as B103), in the Meridian, Mississippi, area WGFB (103.1 FM, "The New B103 - Today's Lite Rock"), in the Rockton, Illinois, area WWOF (103.1 FM, formerly WAIB, "New Country B103"), in the Tallahassee, Florida, area KBIU (103.3 FM, formerly "B103 The B"), in the Lake Charles, Louisiana, area WFXD (103.3 FM, formerly "B103" under its country format), in the Marquette, Michigan, area CKQQ-FM, (103.1 FM, "B-103"), in the Kelowna, British Columbia, area WBDX (103.1 FM, "The New B103, The Outrageous FM!"), in the Trenton, Georgia, area