A floor mat for a vehicle includes an adapter plate for engaging the vehicle's mat retaining system, a mat portion, and a fastener for securing the mat portion to the adapter plate. The configuration of the adapter plate allows the mat portion to be transversely, longitudinally, and rotationally aligned and secured to the vehicle's floor despite variations in the arrangements of different vehicles' mat retaining systems. The mat portion may include a plurality of peripheral guidelines to assist the end-user to trim the mat to fit any intended one of a plurality of automobile models.