  Neutron stars are valuable laboratories for the study of dense matter. Recent
observations have uncovered both massive and low-mass neutron stars and have
also set constraints on neutron star radii. The largest mass measurements are
powerfully influencing the high-density equation of state because of the
existence of the neutron star maximum mass. The smallest mass measurements, and
the distributions of masses, have implications for the progenitors and
formation mechanisms of neutron stars. The ensemble of mass and radius
observations can realistically restrict the properties of dense matter, and, in
particular, the behavior of the nuclear symmetry energy near the nuclear
saturation density. Simultaneously, various nuclear experiments are
progressively restricting the ranges of parameters describing the symmetry
properties of the nuclear equation of state. In addition, new theoretical
studies of pure neutron matter are providing insights. These observational,
experimental and theoretical constraints of dense matter, when combined, are
now revealing a remarkable convergence.
