S81

S81 may refer to:

Aviation

 * Blériot-SPAD S.81, a French fighter aircraft
 * Indian Creek USFS Airport, in Valley County, Idaho, United States
 * Short S.81, an experimental British biplane seaplane

Other uses

 * S81 (New York City bus) serving Staten Island
 * County Route S81 (Bergen County, New Jersey)
 * Daihatsu Hijet (S81), a kei truck and microvan
 * SPANISH SUBMARINE Isaac Peral, a S-80 Plus class submarine
 * Stola S81 Stratos, a concept car
 * S81, a line of the St. Gallen S-Bahn
 * S81, a postcode district for Worksop, England
 * BenQ-Siemens S81, a BenQ mobile phone