R Leonis is a red giant Mira-type variable star in the constellation Leo.

The apparent magnitude of R Leonis varies between 4.31 and 11.65 with a period of 312 days. At maximum it can be seen with the naked eye, while at minimum a telescope of at least 7 cm is needed. The star's effective temperature is estimated between 2930 and 3080 kelvins and radius spans between 320 and 350 solar radii (as large as 1.36–1.5 astronomical units, roughly Mars's orbital zone).