  We use near-infrared interferometric data coupled with trigonometric parallax
values and spectral energy distribution fitting to directly determine stellar
radii, effective temperatures, and luminosities for the exoplanet host stars 61
Vir, $\rho$ CrB, GJ 176, GJ 614, GJ 649, GJ 876, HD 1461, HD 7924, HD 33564, HD
107383, and HD 210702. Three of these targets are M dwarfs. Statistical
uncertainties in the stellar radii and effective temperatures range from 0.5%
-- 5% and from 0.2% -- 2%, respectively. For eight of these targets, this work
presents the first directly determined values of radius and temperature; for
the other three, we provide updates to their properties. The stellar
fundamental parameters are used to estimate stellar mass and calculate the
location and extent of each system's circumstellar habitable zone. Two of these
systems have planets that spend at least parts of their respective orbits in
the system habitable zone: two of GJ 876's four planets and the planet that
orbits HD 33564. We find that our value for GJ 876's stellar radius is more
than 20% larger than previous estimates and frequently used values in the
astronomical literature.
