Abstract: A convertible, self-propelled, motorized mobility assistance device in a plurality of embodiments is provided, comprising a scooter-like chassis (1400) with support deck (300) portion, a handlebar (700), and at least one removable, interchangeable knee rest (800) or seat attachment (1300); wherein the device is mounted atop and driven by at least three motorized wheels (400, 500) which are connected to a source of power and propulsion (1200), and drive (1100). The device further includes a steering system, braking system, and mechanisms for height-adjustability, comfort, and portability.