Silicon photonics allows the large bandwidth of optical communications, which is critical for current long distance networks, to be applied on the scale of a microelectronic chip1,2. By encoding information on multiple wavelength channels through the process of wavelength division multiplexing (WDM), communication bandwidths in excess of 1 Tbit s-1 are possible. Already several optical components critical to WDM networks have been demonstrated in silicon, however a fully integrated multiple wavelength source capable of driving such a network has not yet been realized. Optical amplification, a necessary component for producing a source, can be achieved in silicon through stimulated Raman scattering3,4, parametric mixing5, and the use of silicon nanocrystals6 or nanopatterned silicon7. Furthermore, Raman oscillators have been demonstrated8-10, but the narrow Raman gain window limits operation to a tightly restricted (~ 1 nm) wavelength range and thus is insufficient for WDM. Additionally, electrically pumped light sources11,12 have been implemented by bonding an active III-V layer onto a silicon wafer but the fabrication of these devices is incompatible with current complimentary metal-oxide semiconductor (CMOS) processing. Here we demonstrate the first CMOS-compatible multiple wavelength source by creating an optical parametric oscillator (OPO) formed by a silicon nitride ring resonator coupled to an integrated waveguide. Our device can generate more than 100 new wavelengths, spaced by a few nm, with operating powers below 50 mW. This CMOS-compatible source can form the backbone of a fully operational high-bandwidth optical communications network on a microelectronic chip enabling the next generation of multi-core microprocessors.