The Mercury Cougar is a series of automobiles that was sold by Mercury from 1967 to 2002. The model line is a diverse series of vehicles; though the Cougar nameplate is most commonly associated with two-door coupes, at various stages in its production, the model also was offered as a convertible and a hatchback. During its production as the mid-size Mercury line, the Cougar was also offered as a four-door sedan and five-door station wagon.

In production for 34 years across eight generations (skipping the 1998 model year), the Cougar is second only to the Grand Marquis (36 years) in the Mercury line for production longevity. 2,972,784 examples were produced, making it the highest-selling Mercury vehicle. During the 1970s and 1980s, the marketing of the Mercury division was closely associated with the Cougar, with promotional materials advertising Mercury dealers as "The Sign of the Cat" with big cats atop Lincoln-Mercury dealer signs. Cat-related nameplates were adopted by other Mercury lines, including the Bobcat and Lynx.

During its production, the Cougar was assembled at the Dearborn Assembly Plant (part of the Ford River Rouge Complex) in Dearborn, Michigan from 1967 until 1973, San Jose Assembly (Milpitas, California) from 1968 into early 1969, Lorain Assembly (Lorain, Ohio) from 1974 until 1997, and at Flat Rock Assembly (Flat Rock, Michigan) from 1999 through 2002.

For nearly its entire production, the Cougar followed Mercury tradition, serving as a divisional counterpart of a Ford vehicle. Though sharing a common chassis architecture, the Cougar was visibly distinguished, ranging in degree from distinct grilles, badging, and lighting components to nearly every body panel specific to the model line.

For its first two generations, the Cougar was derived from the Ford Mustang. Initially serving as a pony car, the popularity of the Cougar led it to replace the Cyclone muscle car in the Mercury model line. The second generation moved its market position closer to the personal luxury car segment.

For its third and fourth generations, the Cougar adopted the Ford intermediate chassis. Slotted above the Montego, the model became the counterpart of the Ford (Gran Torino) Elite. For its fourth generation, Mercury split the Cougar into two model lines, with the Cougar replacing the Montego (matching the Ford LTD II), with the Cougar XR7 becoming the counterpart of the Ford Thunderbird (pairing the two models for 20 years).

For its fifth and sixth generations, the Cougar was downsized, adopting the Ford Fox chassis. Replacing the Mercury Monarch, the standard Cougar was the counterpart of the Ford Granada, with the larger Cougar XR7 designed alongside the Ford Thunderbird (sharing its chassis with the Lincoln Continental and Lincoln Mark VII). The sixth generation Cougar (adopting the lineage of the XR7) reverted the line solely to a two-door coupe.

The seventh-generation Cougar introduced the MN12 platform (alongside the Thunderbird). Though again a two-door personal luxury coupe, the model line underwent significant modernization.