Structured illumination microscopy (SIM) is a widely used imaging technique that doubles the effective resolution of widefield microscopes. Most current implementations rely on diffractive elements, either gratings or programmable devices, to generate structured light patterns in the sample. These can be limited by spectral efficiency, speed, or both. Here we introduce the concept of fiber SIM that allows for camera frame rate limited pattern generation and manipulation over a broad wavelength range. Illumination patterns are generated by coupling laser beams into radially opposite pairs of fibers in a hexagonal single mode fiber array where the exit beams are relayed to the microscope objective’s back focal plane. The phase stepping and rotation of the illumination patterns are controlled by fast electro-optic devices. We achieved a rate of 111 SIM frames per second and imaged with excitation patterns generated by both 488 nm and 532 nm lasers.