There's no single definitive answer to the longest production four-door car ever made. The title depends on how you define "length" (wheelbase vs. overall length) and which cars are included (considering only standard production models, excluding limousines or stretched versions). Different sources will list different contenders.
To find the longest, you'd need to meticulously research the overall length specifications of many large sedans and luxury cars throughout history. No readily available, universally agreed-upon database exists to provide this information definitively.
