R Reticuli, also listed under the duplicate variable star designation S Reticuli, is a Mira variable star in the southern constellation Reticulum. It is an aging red giant star on the asymptotic giant branch with a stellar classification that varies between M4e to M7.5e, being hottest near maximum visual magnitude. The brightness of the star varies between apparent visual magnitudes 6.35 and 14.2 with an average period of . The mean maximum magnitude is 7.57 and the mean minimum magnitude 13.80.