The MGA design originated in 1951, when MG designer Syd Enever created a streamlined body for George Philips' TD Le Mans car. This new bodywork traded the MG TF’s articulated fenders and running board for ponton styling. A prototype was initially rejected by BMC chairman Leonard Lord, who had recently signed a deal with Donald Healey, but falling sales of traditional MG models led to a change of heart. The car was named MGA by John Thornley in 1954.
The initial MGA was fitted with the BMC B series straight-4 engine from the MG Magnette saloon, coupled to a four-speed gearbox, producing 68 hp, which was soon uprated to 72 hp. Lockheed hydraulic drum brakes were used on all wheels. The Motor magazine tested an early open car in 1955, recording a top speed of 97.8 mph and 0–60 mph acceleration in 16.0 seconds, at a cost of £844 including taxes. A coupé version was also produced, bringing the total production of standard MGAs to 58,750.
A high-performance Twin-Cam model was introduced in 1958, featuring a high-compression DOHC aluminium cylinder head version of the B-Series engine producing 108 hp, and four-wheel disc brakes by Dunlop. However, the engine proved temperamental, suffering from detonation and oil consumption. Production of the Twin-Cam ended in April 1960 after 2,111 (or 2,210 according to some sources) were produced. The Motor magazine tested an open Twin-Cam in 1958, achieving a top speed of 113 mph and 0–60 mph in 9.1 seconds, costing £1,283 including taxes.
In May 1959, the standard cars received an updated 1588 cc engine producing 79.5 bhp, and front disc brakes were fitted, though drums remained at the rear. The 1600 De Luxe versions were produced with leftover wheels and disc brakes from the Twin-Cam, or using modified Twin-cam chassis. Seventy roadsters and 12 coupés were built as De Luxe models. The Motor tested a 1600 open car in 1959, recording a top speed of 96.1 mph and 0–60 mph in 13.3 seconds, costing £940 including taxes.
Further engine revisions occurred with the 1961 Mark II MGA, increasing the bore to 76.2 mm for a displacement of 1622 cc and increasing horsepower to 90 bhp. The Mark II also featured a higher 4:1 rear axle ratio and an inset grille with horizontal Morris Mini tail lamps. 8,198 Mark II roadsters and 521 coupés were built. Road & Track magazine reported an estimated top speed of 105 mph and 0–60 mph acceleration of 12.8 seconds for the MG A 1600 Mark II in September 1961. As with the 1600, a limited number of Mark II De Luxe versions were produced; 290 roadsters and 23 coupés.
The MGA’s bodywork was based on a one-off MG TD built for George Phillips for the 1951 24 Hours of Le Mans. Three MGA prototypes were entered in the 1955 24 Hours of Le Mans, with two finishing 12th and 17th overall. In the United States, the MGA was raced extensively in Sports Car Club of America competition, winning numerous regional and national championships. Kent Prather was a particularly successful American MGA driver, winning G Production at the SCCA national championships in 1986, 1990, 1995, 2002, 2003, and 2005. The MGA was also used in NASCAR from 1960 to 1963, but failed to win a single race.