A collapsible upright wheeled walker with adjustable armrests that support sufficient user upper-body weight to facilitate a natural upright gait and provide unassisted mobility for a wide range of mobility-impaired individuals. The apparatus may be easily and quickly folded (and unfolded) and may include bilateral stabilizing wheel suspensions to facilitate navigation over uneven terrain. The apparatus includes a frame-stiffening folder assembly and may also include mechanical brakes, an adjustable upper armrest assembly with removable padded forearm supports and two pairs of handles, at least one of which is disposed sufficiently forward to place the user within the polygonal footprint defined by the front and rear wheels to provide support without leaning, stooping, or risking falls.