The Ryan STs were a series of two seat, low-wing monoplane aircraft built in the United States by the Ryan Aeronautical Company. They were used as sport aircraft, as well as trainers by flying schools and the militaries of several countries.

The Ryan Aeronautical Company was founded by T. Claude Ryan in San Diego, California, in 1934. It became part of Teledyne in 1969, and of Northrop Grumman when the latter company purchased Ryan in 1999. Ryan built several historically and technically significant aircraft, including four innovative V/STOL designs, but its most successful production aircraft was the Ryan Firebee line of unmanned drones used as target drones and unmanned air vehicles.