In the past decade, plasmonic resonators have emerged and exploited field compression to create ultrasmall mode volume devices and to enhance light–matter interactions. We devised a ring resonator on a metal substrate separated by a low-permittivity dielectric, which supports hybrid plasmonic modes with a highly localized electromagnetic field. The finite difference time domain method was used to calculate the properties of the ring resonator. By changing the cavity’s geometry and low-permittivity dielectric’s height, a high-quality factor along with ultracompact mode confinement was achieved, leading to Purcell factor as high as 2.7×10 4 . The hybrid plasmonic ring resonator exhibits a trade-off between the high-quality factor and the ultrasmall mode volume at subwavelength scale in the visible spectrum.