  We present an absolute parallax and relative proper motion for the
fundamental distance scale calibrator, RR Lyr. We obtain these with astrometric
data from FGS 3, a white-light interferometer on HST. We find $\pi_{abs} = 3.82
\pm 0.2$ mas. Spectral classifications and VRIJHKT$_2$M and DDO51 photometry of
the astrometric reference frame surrounding RR Lyr indicate that field
extinction is low along this line of sight. We estimate <A_V>=0.07\pm0.03 for
these reference stars. The extinction suffered by RR Lyr becomes one of the
dominant contributors to the uncertainty in its absolute magnitude. Adopting
the average field absorption, <A_V>=0.07 \pm 0.03, we obtain M_V^{RR} = 0.61
^{-0.11}_{+0.10}. This provides a distance modulus for the LMC, m-M = 18.38 -
18.53^{-0.11}_{+0.10} with the average extinction-corrected magnitude of RR Lyr
variables in the LMC, <V(RR)>, remaining a significant uncertainty. We compare
this result to more than 80 other determinations of the distance modulus of the
LMC.

Astrophysics