The manipulation of ultraintense laser beams gets increasingly challenging with growing laser peak power, as the breakdownof conventional optics imposes ever largerbeamdiameters. Using compact plasma-based optical elements to control or even generate such beams1–4 is a promising approach, since plasmas can sustain considerable light intensities.We introduce a new type of plasma optics, called plasma holograms, by initiating plasma expansion on a flat solid target with a holographic prepulse beam focus. A modulated plasma surface then grows out of the target after ionization, which can be used for several picoseconds to diffract and spatially shape ultraintense laser beams. On the basis of this concept, we demonstrate the generation of fork plasma gratings, which we use to induce optical vortices on a femtosecond laser beam as well as its high-order harmonics, at intensities exceeding 10$^{19}$W cm$^{-2}$. These plasma holograms open up a whole new range of possibilities for the manipulation of ultraintense lasers and the generation of structured coherent short-wavelength sources.