  The Sigma^- mean squared charge radius has been measured in the space-like
Q^2 range 0.035-0.105 GeV^2/c^2 by elastic scattering of a Sigma^- beam off
atomic electrons. The measurement was performed with the SELEX (E781)
spectrometer using the Fermilab hyperon beam at a mean energy of 610 GeV/c. We
obtain <r^2> = (0.61 +/- 0.12 (stat.) +/- 0.09 (syst.)) fm^2. The proton and
pi^- charge radii were measured as well and are consistent with results of
other experiments. Our result agrees with the recently measured strong
interaction radius of the Sigma^-.
