前蘇聯未來前線戰鬥機計劃（PFI），氣動外形流暢，機動性能卓越，雙發、全天候、重型戰鬥機，蘇愷-27戰鬥機（Su-27）「側衛」

蘇愷-27戰鬥機（俄語：Cy-27，拉丁字母轉寫 Su-27）是在前蘇聯時期由蘇愷設計的雙發、全天候、重型戰鬥機。其北約代號為側衛（Flanker）。蘇愷-27由前蘇聯研製，設計目的是為對抗1970年代美軍發展的戰鬥機，主要假想敵是F-15。設計要求長航程、重武裝及重視操控靈活性。蘇愷-27除了擔任空優任務為主的機型之外，還有其他多種任務的衍生型。依照當代之戰機世代劃分，屬於第四代戰機。
The Sukhoi Su-27 (Russian: Сухой Су-27; NATO reporting name: Flanker) is a Soviet-origin twin-engine supermaneuverable fighter aircraft designed by Sukhoi. It was intended as a direct competitor for the large United States fourth-generation fighters such as the Grumman F-14 Tomcat and McDonnell Douglas F-15 Eagle, with 3,530-kilometre (1,910 nmi) range, heavy aircraft ordnance, sophisticated avionics and high maneuverability. The Su-27 was designed for air superiority missions, and subsequent variants are able to perform almost all aerial warfare operations. It was designed with the Mikoyan MiG-29 as its complement.