  Using Hubble Space Telescope (HST) photometry, we characterize the age of the
stellar association in the vicinity of supernova (SN) 2011dh and use it to
infer the zero-age main sequence mass (M_{ZAMS}) of the progenitor star. We
find two distinct and significant star formation events with ages of <6 and
17^{+3}_{-4} Myrs, and the corresponding M_{ZAMS} are >29 and 13^{+2}_{-1}
M_{Sun}, respectively. These two bursts represent 18^{+4}_{-9}% (young) and
64^{+10}_{-14}% (old) of the total star formation in the last 50 Myrs. Adopting
these fractions as probabilities suggests that the most probable M_{ZAMS} is
13^{+2}_{-1} M_{Sun}. These results are most sensitive to the luminosity
function along the well-understood main sequence and are less sensitive to
uncertain late-stage stellar evolution. Therefore, they stand even if the
progenitor suffered disruptive post-main-sequence evolution (e.g. eruptive mass
loss or binary Roche-lobe overflow). Progenitor identification will help to
further constrain the appropriate population. Even though pre-explosion images
show a yellow supergiant (YSG) at the site of the SN, panchromatic SN light
curves suggest a more compact star as the progenitor. In spite of this, our
results suggest an association between the YSG and the SN. Not only was the
star located at the SN site, but reinforcing an association, the star's
bolometric luminosity is consistent with the final evolutionary stage of the 17
Myr old star burst. If the YSG disappears, then M_{ZAMS}=13^{+2}_{-1} M_{Sun},
but if it persists, then our results allow the possibility that the progenitor
was an unseen star of >29 M_{Sun}.
