‘Neptune’ (Reg. No. CV‐132, PI 655959) is a southern medium‐grain rice (Oryza sativa L.) developed at the Rice Research Station, Louisiana State University Agricultural Center (LSU AgCenter), Crowley, LA, and officially released in December 2007. It was developed from a single cross using the pedigree selection procedure. Neptune was tested under the experimental designation RU0402028 in the Louisiana Commercial Advanced (CA) yield test trial at seven locations, as well as in the Uniform Regional Rice Nursery (URRN) in Arkansas, Louisiana, Missouri, Mississippi, and Texas from 2004 to 2007. Neptune is a high‐yielding, moderately early‐maturing, semidwarf cultivar with excellent milling quality, exceptional ratoon yield potential, good lodging resistance, and favorable large grain size. In 41 trials replicated statewide in Louisiana and in multistate URRN, Neptune had the average main and ratoon crop yield of 9.30 and 2.93 t ha−1, respectively. When averaged across years and locations, Neptune had a head rice yield of 62.9% and a total milled rice yield of 70.3%. Under both artificial inoculation and natural infection, Neptune was found to be moderately susceptible to sheath blight (caused by Rhizoctonia solani J.G. Kühn) and the physiological disorder straighthead but moderately resistant to blast (caused by Pyricularia grisea Sacc.) and bacterial panicle blight [caused by Burkholderia glumae (Kurita and Tabei 1967) Urakami et al. 1994. Neptune should well adapt to the Gulf and mid‐south rice growing regions.