Overview: The 5mJy Unbiased Spitzer Extragalactic Survey (5Muses) is a mid-infrared spectroscopic survey of 330 galaxies with the Infrared Spectrograph (IRS) aboard Spitzer. 5MUSE bridges the gap between the bright, nearby infrared galaxies known before Spitzer, and the much fainter, more distant sources which have been the focus of much of the dedicated Spitzer IRS follow-up to date. The legacy of the 5Muses survey is a library of high quality IRS spectra that will be critical for providing: (1) a statistically complete accounting of the relative contribution of stars and AGN in IR-bright galaxies; (2) an overview of the prevailing physical conditions in the dusty ISM in galaxies over the past 2-5 Gyr; (3) proper modeling of the number counts and backgrounds in the infrared out to z=1, and a critical resource for future missions like WISE, Herschel and JWST. 5Muses is a Spitzer Legacy Science program led by IPAC’s director George Helou and a diverse team of scientists at IPAC.