Experimental heat transfer data are presented and a dimensionless correlation developed for natural convection from heated horizontal stationary isothermal circular disks over a wide range of the Rayleigh numbers. Experiments with air were performed for a variety of disks of different diameters and thickness-to-diameter aspect ratios. The significant volume of data is consistent with the single set of data available in the archival literature, and is correlated with a classical Nusselt-Rayleigh correlation.