A multi-purpose detachable blade utility knife includes a handle with a forward and rearward section, divided by a mid-line sagittal plane. The forward section has a body portion and a removable blade cover, along with a forward-facing blade insertion slot. The rearward section features a blade storage compartment that pivots at the rear end. The knife accommodates a notched cutting blade with U-shaped retention notches and a slotted cutting blade with a blade retention slot. A blade retention mechanism in the forward section uses spring-activated push-button mechanisms to secure either blade in an extended cutting position.

A blade retention mechanism is provided including a blade clamp having a lever portion and a protrusion portion coupled to a first end of the lever portion. The lever portion rotates at the first end of the lever portion between a first open position and a second closed position. The protrusion portion of the blade clamp defines an over-center cam that presses a blade into a blade holder of a knife when the lever portion is rotated into the second closed position.