We demonstrate, for the first time to our knowledge, a longitudinally diode-pumped, monolithic ytterbium ion-doped YAG non-planar ring laser (NPRO). We achieved a continuous-wave (cw) single-frequency output power of 1 W with 45.0% slope efficiency and a beam quality factor of M(2)<1.1. In view of iodine frequency stabilization we have characterized the frequency tuning properties and have measured the relative intensity noise. Additionally, 6.1 mW second harmonic power at 515 nm was achieved using a periodically poled KTP crystal in a single-pass setup.