  We use a new redshift survey complete to m_R=15.4 within 4.25 deg from the
center of the Coma cluster to measure the mass profile of the cluster to r=5.5
Mpc/h. We extend the profile to r=10 Mpc/h with a further sample complete to
m_R=15.4 in 42% of the area within a 10 deg radius and to m_{Zw}=15.5 in the
remaining area. Galaxies within this region are falling onto the cluster on
moderately radial orbits and thus do not satisfy virial equilibrium.
Nonetheless, identification of the caustics in redshift space provides an
estimate of the gravitational potential at radius r and hence of the system
mass, M(<10 Mpc/h)=(1.65+-0.41)10^{15} M_\odot/h (1-sigma error). Previous mass
estimates derived from optical and X-ray observations are limited to r<2.5
Mpc/h. Our mass profile is consistent with these estimates but extends to
distances four times as large. Over the entire range, the mass increases with r
at the rate expected for a Navarro, Frenk & White (1997) density profile.
