The bright star 55 Cancri is known to host five planets, including a transiting super-Earth. We use the CHARA Array to directly determine the following of 55 Cncs stellar astrophysical parameters: $R=0.943 pm 0.010 R_{odot}$, $T_{rm EFF} = 5196 pm 24$ K. Planet 55 Cnc f ($M sin i = 0.155 M_{Jupiter}$) spends the majority of the duration of its elliptical orbit in the circumstellar habitable zone (0.67--1.32 AU) where, with moderate greenhouse heating, it could harbor liquid water. Our determination of 55 Cancris stellar radius allows for a model-independent calculation of the physical diameter of the transiting super-Earth 55 Cnc e ($simeq 2.1 R_{earth}$), which, depending on the assumed literature value of planetary mass, implies a bulk density of 0.76 $rho_{earth}$ or 1.07 $rho_{earth}$.
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