We demonstrate a prism-based pulse shaping setup that enables the shaping of ultrashort pulses with octave-spanning spectra. In contrast to gratings prisms allow for a high throughput and large bandwidths. The second-order dispersion of the prism material is precompensated by a fused silica prism sequence while higher dispersion orders are compensated by the pulse shaper. This flexible tool for dispersion compensation enables us to generate the shortest pulses ever achieved directly from an oscillator. The resulting pulse is almost transform-limited and shows a clean temporal profile with very low background. We assess the performance and limitations of the setup both experimentally and by theoretical analysis.