High resolution observations of the extended atmospheres of asymptotic giant branch ( AGB ) stars can now directly confront the theories that describe stellar mass loss . Using Atacama Large Millimeter/submillimeter Array ( ALMA ) high angular resolution ( 30 \times 42 mas ) observations we have , for the first time , resolved stellar rotation of an AGB star , R Dor . We measure an angular rotation velocity of \omega _ { R } \sin { i } = ( 3.5 \pm 0.3 ) \times 10 ^ { -9 } rad s ^ { -1 } which indicates a rotational velocity of | \upsilon _ { rot } \sin { i } | = 1.0 \pm 0.1 km s ^ { -1 } at the stellar surface ( R _ { * } = 31.2 mas at 214 GHz ) . The rotation axis projected on the plane of the sky has a position angle \Phi = 7 \pm 6 ^ { \circ } . We find that the rotation of R Dor is two orders of magnitude faster than expected for a solitary AGB star that will have lost most of its angular momentum . Its rotational velocity is consistent with angular momentum transfer from a close companion . As a companion has not been directly detected we thus suggest R Dor has a low-mass , close-in , companion . The rotational velocity approaches the critical velocity , set by the local sound speed in the extended envelope , and is thus expected to affect the mass loss characteristics of R Dor .