The modular backpack and harness system is a modular backpack. The modular backpack and harness system is interchangeable such that the modular backpack and harness system can be adjusted to the cargo being carried by the modular backpack and harness system. The modular backpack and harness system incorporates a harness structure and a plurality of cargo structures. Each cargo structure selected from the plurality of cargo structures removably attaches to the harness structure. The plurality of cargo structures are interchangeable. The difference between any first cargo structure selected from the plurality of cargo structures and any second cargo structure selected from the plurality of cargo structures is the cargo the selected cargo structures are configured to carry.

A combination chair and pack frame apparatus for alternately seating a user and supporting loads on the user's back includes a seat frame mounted on a main frame. The seat frame may be folded against the main frame, placed in a seat position, or placed in a pack position. A seat made of flexible material is attached to the main frame and a distal portion of the seat frame relative to the main frame. When the seat frame is in the seat position, the seat may be sat on. When the seat frame is in the pack position, a load may be supported on the seat. A harness mounts the main frame to the user's back when the seat frame is in the pack position. A support leg assembly selectively supports the main frame when the seat frame is in the seat position.

A combination chair and pack frame apparatus for alternately seating a user and supporting loads on the user's back includes a seat frame mounted on a main frame. The seat frame may be folded against the main frame, placed in a seat position, or placed in a pack position. A seat made of flexible material is attached to the main frame and a distal portion of the seat frame relative to the main frame. When the seat frame is in the seat position, the seat may be sat on. When the seat frame is in the pack position, a load may be supported on the seat. A harness mounts the main frame to the user's back when the seat frame is in the pack position. A support leg assembly selectively supports the main frame when the seat frame is in the seat position.