The present invention is directed to a bi-folding wheelchair (10) with side frames (12) and (14) that fold together with a compound scissor action moving the large rear wheels (96) to a central location while the backrest (50) is folding downwardly. Two separate locking mechanisms (28) and (40) hold the frame apart in the upright position while two additional locking mechanisms (77) hold the backrest (50) upright or down in the collapsed position. All the major components of the conventional wheelchairs like the foot rests, the arm rests, large wheels, caster wheels and the backrest fit into a compact package narrower than the unfolded wheelchair and slightly larger than the diameter of the back wheels with all parts folding in and out simultaneously. The large rear wheel assemblies can be quickly removed further reducing the size and weight of the device for shipping or storage.