The X-Shooter Spectral Library (XSL) in the optical -- First year of the survey

We present the first release of XSL, the X-Shooter Spectral Library. This release contains 239 stars spanning the wavelength 3000--10200 Å observed at a resolving power R ≡ λ / Δλ ˜ 10000. The spectra were obtained at ESO's 8-m Very Large Telescope (VLT). The sample contains O -- M, long-period variable (LPV), C and S stars. The spectra are flux-calibrated and telluric-corrected. We describe a new technique for the telluric correction. The wavelength coverage, spectral resolution and spectral type coverage of this library make it well suited to stellar population synthesis of galaxies and clusters, kinematic investigation of stellar systems and studying the physics of cool stars.