Room temperature single photon emitters are very important resources for photonics and emerging quantum technologies. In this work we study single photon emission from defect centers in 20 nm zinc oxide (ZnO) nanoparticles. The emitters exhibit bright broadband fluorescence in the red spectral range centered at 640 nm with polarized excitation and emission. The studied emitters showed continuous blinking, however, bleaching can be suppressed using a polymethyl methacrylate (PMMA) coating. Furthermore, hydrogen termination increased the density of single photon emitters. Our results will contribute to the identification of quantum systems in ZnO.Sources of non-classical light, are important for a range of applications in quantum communications, sensing and information processing 1, 2 . A particular emphasis is placed on the development of solid-state single photon sources that operate at room temperature, as those are the most promising sources for scalable and integrated devices. Color centers in diamond 3 , and in particular the nitrogen vacancy 4 and the silicon vacancy defects 5,6 , have been the subject of intense study in recent years due to their unprecedented photostability and spin properties. Recently, several additional materials have emerged as candidates for single photon generation, including site controlled GaN quantum dots 7 , defects in silicon carbide 8 and zinc oxide (ZnO) 9 . While the single photon emission in SiC is attributed to the intrinsic defect known as an "antisite -vacancy pair", the origin of the quantum emission in ZnO remains under debate. ZnO offers an interesting and valuable system to study quantum effects at the nanoscale 10 . ZnO nanoparticles are commercially available while nanowires and other nanostructures can be easily synthesized by hydrothermal 11 or chemical vapour deposition growth techniques 12,13 . In addition, ZnO is very suitable for photonic applications, as it has a wide, direct bandgap (3.4 eV) and a large number of intrinsic defects and impurities that emit from the ultraviolet to the near infrared 14,15 . Finally, photonic elements including microdisk cavities 11,16,17 can be easily fabricated from this material. Therefore, there is an urgency to understand and