  Type IIb supernovae are important subclass of stripped-envelope supernovae
(SNe), which show H lines only at early times. Their progenitors are believed
to contain a low-mass H envelope before explosion. This work reports the
discovery of a progenitor candidate in pre-explosion Hubble Space Telescope
images for the Type IIb SN~2017gkk. With detailed analysis of its spectral
energy distribution and local environment, we suggest that the progenitor is
most likely a yellow supergiant with significant circumstellar extinction and
has an initial mass of about 16 $M_\odot$, effective temperature log($T_{\rm
eff}/K)=3.72\pm0.08$ and luminosity log($L/L_{\odot})=5.17\pm0.04$. This
progenitor is not massive enough to strip envelope through stellar wind, and it
supports an interacting binary progenitor channel and adds to the growing list
of direct progenitor detections for Type~IIb SNe. Future late-time observations
will confirm whether this progenitor candidate has disappeared and reveal the
putative binary companion that has survived the explosion.
