Three distinct generations were available during its 35-year production run until it was replaced in 1999 with the Proudia in an attempt to continue to offer a top-level luxury sedan.

[2] Aside from a very minor export push in the 1960s, the Debonair was mainly sold in Japan, although the second and third generations met with considerable success in South Korean license production.

As a result of the Debonair's perceived primary purpose as a "senior executive vehicle", it did not undergo regular improvements to its exterior appearance, while the mechanicals were routinely updated with the latest advancements as the years progressed.

The Debonair was Mitsubishi's competitor to the Nissan Cedric, Prince Gloria, Isuzu Bellel and Toyota Crown, and during the first generation's production, the appearance remained generally unchanged from 1964 until 1986, sharing a tradition with the Toyota Century, that being also recognized as a senior executive sedan exclusive to the Japanese market.

Although it received several minor redesigns (denoted I through IV), the vehicle proved popular enough in the Japanese market to remain in production for 22 years without major appearance modifications.

The Debonair was largely the result of former General Motors designer Hans S. Bretzner,[4] while the result was largely influenced by the 1961 Lincoln Continental designed by Elwood Engel, as evidenced by the slab-sided body panels, squared wheel wells, extended protrusions at the front of the vehicle, wraparound turn signals in the front, and tapered fins at the rear, with a rear taillight cluster, exhibiting a "Continental-esque" appearance.

Powered initially by the KE64 1,991 cc six-cylinder engine with twin carburetors and dual exhausts, the original A30 series developed 105 PS (77 kW; 104 hp) at 5,000 rpm, and had a maximum speed of 155 km/h (96 mph).

When the 4G54 "Astron" (2,555 cc) four-cylinder engine was introduced June 1976, the trim package was renamed "Executive SE" and the model code became A32.

The second-generation Debonair adopted a front-wheel drive layout, a cost-effective way to increase interior space without investing money on engineering in an executive sedan, shared with the E11 Galant.

[7] A 150 PS (110 kW; 148 hp) supercharged version of the 2.0-liter engine was added to the lineup in February 1987,[9][11] using the world's first needle roller rocker arm assembly.

The Roman numeral identification approach was also used on Mitsubishi's top-of-the-line sports car, the Starion to identify specific trim packages.

The motivation to introduce a modern looking, executive level luxury sedan also took place in what has become known as the Japanese asset price bubble period that began after the Plaza Accord agreement in 1985.

German tuner AMG was brought in to enhance this version of the Debonair, which primarily consisted of exterior body treatments.

[15] Even after the introduction of the more modern Diamante, the Debonair underwent one last facelift, mostly in order to update the passive safety of the car.

Some of the technologies used were: In July 1993, a limited edition, long wheelbase model called the Debonair 150 (as it was extended by 150 mm) was added to the lineup.

As this generation was Mitsubishi's flagship model, the body style that was compliant with Japanese government regulations concerning exterior dimensions and engine displacement was no longer offered.

However, Mitsubishi also developed its first V8 engine for the Dignity limousine around this time, and it was this latter model which took position as the domestic flagship of the company.