Differential cross sections have been measured for large-angle p−p elastic scattering at intermediate momenta in an experiment performed at the Argonne National Laboratory Zero Gradient Synchrotron. A wire-spark-chamber detection system was employed. The results are reported at 13 momenta between 1.5 and 5.5 GeVc, and cover the angular region 30≤θc.m.≤90°. The statistical accuracy of the data, presented in 2° bins in θc.m., is typically ±4%. The data suggest slope changes in the fixed-θc.m. cross sections near −t=0.8 and 3 (GeVc)2. The results of attempts to interpret the data in terms of optical models, the statistical model, the Regge-pole model, and a diffractive model are presented. A Regge calculation which predicts the masses at which dibaryon resonances might be expected to occur is outlined.