Designed as a successor to the 35 Draken, the Saab 37 Viggen (Thunderbolt) was the result of a Swedish requirement to incorporate a variety of diferent roles in a single airframe, this would fit the needs of the air defense of the country in tandem with the STRIL 60 electronic air-defense control system adopted nationwide. As such, the Viggen became Sweden's first true attempt to create a full weapons system in which the avionics, powerplant and weapons would be just as important as the aircraft itself; it was also the first major combat aircraft in the world to incorporate the canard-delta wing configuration which permits a certain degree of STOL capability. The initial model of the Viggen was designed primarily as an all-weather attack aircraft, this was subsequently followed by the reconnaissance and interceptor versions the latter which was also Europe's first aircraft with a pulse-Doppler radar. The Viggen is currently being replaced by the 39 Gripen in Swedish service with no other foreign operators due to highly restrictive export controls and the interference of larger nations such as the US in blocking potential sales.

The first prototype AJ 37 was flown on 8 February 1967 and entered service in 1971. The AJ 37 had provision for a wide variety of both air-to-air and air-to-ground munitions although its main purpose was ground attack (hence the AJ designation). A variety of reconnaissance variants were also produced, these included the armed recon SF 37 with full weapons capability (but without radar) and the SH 37 maritime recon model with provisions for ant-ship strike. The most important variant of the Viggen, however, was the JA 37 interceptor with secondary attack capability. Based on the Ericcson long-range pulse-Doppler radar, it had one of the most advanced avionics sets of its time and also included more powerful engines than the AJ 37. A tandem two-seater trainer is known as the Sk 37 and a major upgrade in over one hundred Swedish units resulted in the AJS 37 with full multi-role capability plus new weapons and avionics.