The Rumpler B.I (factory designation 4A) was a military reconnaissance aircraft produced in Germany during World War I.
The B.I was a conventional two-bay biplane with unstaggered wings of unequal span. It featured two open cockpits in tandem and fixed, tailskid undercarriage. Its upper wing reflected the wing design of the Etrich Taube that Rumpler was building at the time.
Rumpler built 198 of these aircraft for the Luftstreitkräfte, plus 26 seaplane versions for the Imperial German Navy.