Red grapefruit is a common cultivar of the grapefruit.
Red grapefruit was discovered as a sport growing on a pink variety and was patented in 1929 as the "Ruby Red" (or "Redblush") cultivar. Subsequent cultivars of red grapefruit were developed in part with radiation-triggered mutations, leading to the Rio Red, Rio Star, and Ruby-Sweet varieties.
The Ruby Red grapefruit was designated the official State Fruit of Texas in 1993.