Several nearby red giant and supergiant stars have been resolved with 4-m telescopes, producing a number of significant results. Angular diameter measurements have provided evidence for first-overtone pulsation in Mira variables [Tuthill et al.1994b, Haniff et al. 1995] and produced a new T(eff) versus (J-K) relation [Feast 1996]. Also important are the discoveries of hotspots on Ori (Betelgeuse) by Buscher et al. 1990 and of asymmetries in the atmosphere of o Cet and similar stars [Wilson et al. 1992, Haniff et al. 1992, Tuthill et al. 1994a].
It has long been assumed that Ori, a red supergiant, has the largest angular diameter of any star in the night sky. Here we report measurements of the red giant R Doradus (HR 1492), a semiregular variable of spectral type M8, which show it to exceed Ori in angular size. Although the V magnitude of R Dor is only 5.4, at infrared wavelengths it rivals Ori as the brightest star in the sky. This has lead Wings 1971 to predict a large angular size but R Dor has not previously been observed at high angular resolution, presumably due to its southerly declination. We also report observations of W Hydrae (HD 120285), which is a small-amplitude Mira variable that also has a large angular diameter.