  We use a time-dependent hydrodynamic code and a non-LTE Monte Carlo code to
model disk dissipation for the Be star 66 Ophiuchi. We compiled 63 years of
observations from 1957 to 2020 to encompass the complete history of the growth
and subsequent dissipation of the star's disk. Our models are constrained by
new and archival photometry, spectroscopy and polarization observations,
allowing us to model the disk dissipation event. Using Markov chain Monte Carlo
methods, we find 66 Oph is consistent with standard B2Ve stellar properties. We
computed a grid of 61568 Be star disk models to constrain the density profile
of the disk before dissipation using observations of the H$\alpha$ line profile
and SED. We find at the onset of dissipation the disk has a base density of
$2.5\times10^{-11}\ \rm{g\ cm^{-3}}$ with a radial power-law index of $n=2.6$.
Our models indicate that after 21 years of disk dissipation 66 Oph's outer disk
remained present and bright in the radio. We find an isothermal disk with
constant viscosity with an $\alpha = 0.4$ and an outer disk radius of $\sim$115
stellar radii best reproduces the rate of 66 Oph's disk dissipation. We
determined the interstellar polarization in the direction of the star in the
V-band is $p=0.63 \pm 0.02\%$ with a polarization position angle of
$\theta_{IS}\approx85.7 \pm 0.7^\circ$. Using the Stokes QU diagram, we find
the intrinsic polarization position angle of 66 Oph's disk is
$\theta_{int}\approx98 \pm 3^\circ$.
