STELIB is a new spectroscopic stellar library, available at http://webast.ast.obs-mip.fr/stelib . It consists in an homogeneous library of stellar spectra in the visible range (3200 to 9500){AA}), with an intermediate spectral resolution (<~3{AA}) and sampling (1{AA}), and corrected from interstellar absorption. This library includes 255 stars of various spectral types and luminosity classes, spanning a relatively wide range in metallicity. The spectral resolution, wavelength and spectral type coverage of this library represents a substantial improvement over previous libraries used in population synthesis models. The overall absolute photometric uncertainty is 3%. The data were obtained during two runs, one at the 1m Jacobus Kaptein Telescope (JKT), Roque de los Muchachos Observatory, La Palma, Canary Islands, Spain, between 1994 March 28 and April 4, and a second one at the 2.3m of the Australian National University at Siding Spring (SSO), Australia, between 1994 December 25 and 31.