Technical Abstract: ‘Rex’ (Oryza sativa L.) (Reg. No. CV-136, PI 661111) is a conventional, southern, long-grain rice cultivar developed at the Mississippi Agricultural and Forestry Experiment Station, Delta Research and Extension Center, Stoneville, MS, and officially released in February 2010. Rex is a semidwarf cultivar with good straw strength, good standability, and good milling, and it exhibits exceptional and stable yield performance. Rex was tested in Arkansas, Louisiana, Mississippi, Missouri, and Texas in a total of 35 environments from 2006 to 2010. Averaged over the 35 replicated trials, Rex had an average grain yield of 10.16 t ha-1. Its consistency in grain yields across production sites and years can be contributed, in part, to its excellent straw strength as shown by a lodging incidence of less than 1% over the same number of environments. Furthermore, Rex averaged a whole milling yield of 579 g kg-1 and a total milling yield of 692 g kg-1. While Rex is susceptible to rotten neck blast [caused by Pyricularia grisea (Cooke) Sacc.] and sheath blight disease (caused by Rhizoctonia solani J.G. Kühn), its level of field tolerance has permitted its overall field performance to match or numerically exceed the performance of other similar susceptible varieties. Rex should be well adapted to the growing conditions found in the southern USA.