We present the detection of the progenitor of the Type II SN 2011dh in archival pre-explosion Hubble Space Telescope images .
Using post-explosion Adaptive Optics imaging with Gemini NIRI+ALTAIR , the position of the SN in the pre-explosion images was determined to within 23 mas .
The progenitor object was found to be consistent with a F8 supergiant star ( \mathrm { log } L / L _ { \odot } = 4.92 \pm 0.20 and T _ { eff } = 6000 \pm 280 K ) .
Through comparison with stellar evolution tracks , this corresponds to a single star at the end of core C-burning with an initial mass of M _ { ZAMS } = 13 \pm 3 M _ { \odot } .
The possibility of the progenitor source being a cluster is rejected , on the basis of : 1 ) the source is not spatially extended ; 2 ) the absence of excess \mathrm { H \alpha } emission ; and 3 ) the poor fit to synthetic cluster SEDs .
It is unclear if a binary companion is contributing to the observed SED , although given the excellent correspondence of the observed photometry to a single star SED we suggest the companion does not contribute significantly .
Early photometric and spectroscopic observations show fast evolution similar to the transitional Type IIb SN 2008ax , and suggest that a large amount of the progenitor ’ s hydrogen envelope was removed before explosion .