The Shelby Mustang is a high performance variant of the Ford Mustang which was built by Shelby American from 1965 to 1968, and from 1969 to 1970 by Ford. Following the introduction of the fifth generation Ford Mustang in 2005, the Shelby nameplate was revived as a new high-performance model, this time designed and built by Ford.

The 1965–1966 cars were the smallest and lightest of the GT 350 models. These cars are often called "Cobras", which was the Ford-powered AC-based two-seat sports car also produced by Shelby American during the same period. Both models use the Cobra emblem, similar paint scheme, and the optional "Cobra" valve covers on many GT350s that were part of a marketing tie-in by Shelby, as well as one of his iconic symbols. All 1965–66 cars featured the Windsor 289 cu in (4.7 L) HiPo K-Code 271 hp (202 kW; 275 PS) V8 engine, modified with a large 4-barrel Holley 715 CFM carburetor to produce 306 bhp (310 PS; 228 kW) @ 6000 rpm and 329 lb⋅ft (446 N⋅m) @ 4200 rpm of torque.[2][3] Marketing literature referred to this engine as the "Cobra hi-riser" due to its high-riser intake manifold. Beginning as a stock Mustang with a 4-speed manual transmission and 9" live rear axle, the cars were shipped to Shelby American, where they received the high-riser manifolds, Tri-Y headers, and were given larger Ford Galaxie rear drum brakes with metallic-linings and Kelsey-Hayes front disc brakes.

The 1965 GT350 was not built for comfort or ease of driving. There were 34 "GT350R" race-spec cars built specifically for competition use under SCCA rules, and the model was the B-Production champion for three straight years.[4] The 1966 GT350 had featured more comfort of casual drivers that included rear seats, optional colors, and an optional automatic transmission. This trend for additional features continued in following years, with the cars becoming progressively larger, heavier, and more comfortable, while losing much of their competitiveness in the process. The 1969 GT350s and GT500s were largely styling modifications to a stock Mustang. By 1969 Carroll Shelby was no longer involved in the Shelby GT program, and the design was done in-house by Ford.

The 1965 and 1966 GT350s were delivered from Ford's San Jose Assembly Plant in body in white form for modification by Carroll Shelby's operation, originally in Venice Beach and later at Los Angeles International Airport. San Jose cars carried an "R" in the Ford VIN denoting that facility.[5] The only year that Shelby Mustangs from the 1960s came from another plant was 1968, where they came from New Jersey, "T" in the VIN,[6] and were modified by A.O. Smith