The LaGG-3-66 was a final and most advanced variant of the LaGG-3, a Soviet single-engine fighter designed by the OKB-301 design team (S. Lavochkin, V. Gorbunov, and M. Gudkov). The 66 series aircraft had the best flight characteristics of all the LaGG-3s. It was upgraded with a lighter frame and 55 mm bulletproof glass, among other improvements. Production of the 66 series took place from spring 1943 to July 1944 at Plant No. 31 in Tbilisi. About 1,000 66 series aircraft were built in total. LaGG-3s were used extensively by the Soviet Air Force during World War II and also saw combat against Japan in 1945.

The LaGG-3-66 was introduced in Update 1.31. Like the previous series of the aircraft, it has powerful armament, but now with addition of thick armored glass to protect the pilot in head-on attacks. Another distinctive feature of the 66 series aircraft is their improved maneuverability. While the German Bf 109s and other high-altitude fighters are superior to the LaGG-3 at high altitudes, this fighter can also be a formidable opponent at low altitudes (up to 3,000 meters) when flown by an experienced pilot.