A mechanically activated bypass valve apparatus for allowing fluid being pumped through the pipe or coiled tubing string to be bypassed around a tool string and into the wellbore. Activation of the bypass valve is accomplished by applying weight-on-bit to the apparatus to shear a set of shear screws, allowing the mandrel to move axially relative to the tubular housing. Lowering the pipe string and setting down weigh on bit misaligns fluid bypass ports in the mandrel and housing, thus forcing fluid to continue to flow through the bore of the tool and to the toolstring below the bypass tool. Picking up on the pipe string aligns corresponding ports in the mandrel and housing and allows fluid to flow from the bore of the tool to the wellbore annulus, thus bypassing other tools downhole of the apparatus.