  We present deep Hubble Space Telescope imaging of the nearby Type Ia
supernova (SN Ia) 2011fe obtained 11.5yr after explosion. No emission is
detected at the SN location to a $1\sigma$ ($3\sigma$) limit of ${F555W > 30.2
\;(29.0)}~$mag, or equivalently $M_V > 1.2 \;(-0.1)~$mag, neglecting the
distance uncertainty to M101. We constrain the presence of donor stars impacted
by the SN ejecta with the strictest limits thus far on compact (i.e., $\log \,g
\gtrsim 4$) companions. H-rich zero-age main-sequence companions with masses
$\geq 2~\rm M_\odot$ are excluded, a significant improvement upon the
pre-explosion imaging limit of $\approx 5~\rm M_\odot$. Main-sequence He stars
with masses $\geq 1~\rm M_\odot$ and subgiant He stars with masses $\lesssim
0.8~\rm M_\odot$ are also disfavored by our late-time imaging. Synthesizing our
limits on post-impact donors with previous constraints from pre-explosion
imaging, early-time radio and X-ray observations, and nebular-phase
spectroscopy, essentially all formation channels for SN2011fe invoking a
non-degenerate donor star at the time of explosion are unlikely.
