A multi-purpose air mattress apparatus is disclosed for use in at least a bed of a vehicle having an opposing pair of inwardly protruding wheel wells. The apparatus comprises, in one embodiment, an inflatable air mattress having a pair of opposing sidewalls, each defining a lateral recess sized for accepting at least a portion of the wheel wells therewithin and further defining recess ledges that selectively sit atop the wheel wells. With the apparatus positioned within the vehicle bed and the wheel wells positioned at least partially within the lateral recesses, the recess ledges in combination with a perimeter ledge cover substantially any exposed portions of the wheel wells, while a set of upper and lower perimeter chambers further maintain a stable structure of the apparatus during use both within a vehicle bed as well as on any other relatively flat surface in otherwise conventional fashion.