The Rumpler C.IV was a German single-engine, two-seat reconnaissance biplane. The C.IV was a development of C.III with different tail surfaces and using a Mercedes D.IVa engine in place of C.III's Benz Bz.IV. In addition to the parent company, the aircraft was also built by Pfalz Flugzeugwerke as the Pfalz C.I. Another variant of the basic design was the Rumpler 6B-2 single-seat floatplane fighter, with a 120 kW (160 hp) Mercedes D.III engine, built for the Kaiserliche Marine (Imperial Navy).
For a two-seater reconnaissance aircraft, Rumpler C.IV had an excellent performance, which enabled it to remain in front-line service until the end of World War I on the Western Front, as well as in Italy and Palestine. Its exceptional ceiling allowed pilots to undertake reconnaissance secure in the knowledge that few allied aircraft could reach it.
300 aircraft were licence-built by Pfalz Flugzeugwerke as the Pfalz C.I, differing in ailerons on all four wings. From February 1917 they were renamed Rumpler C.IV (Pfal).
C4, C04, C.IV, C-4, or C-04 may refer to: