The Cosmic Origins Spectrograph (COS) is a new instrument for the Hubble Space Telescope that will be installed during servicing mission 4, currently scheduled for March 2004. The primary science objectives of the mission are the study of the origins of large scale structure in the universe, the formation, and evolution of galaxies, the origin of stellar and planetary systems and the cold interstellar medium. As such, COS has been designed for the highest possible sensitivity on point sources, while maintaining moderate (λ/Δλ = 20,000) spectral resolution. In this paper, the instrument design and predicted performance is summarized, as well as summary of the instrument flight and prototype component performance to date.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.