Abstract: This invention relates to internal concentric shaft disconnect mechanism for use in an integrated drive generator of the type employed onboard aircraft for power generation. The integrated drive generator employs a concentric input shaft/output shaft arrangement wherein it is desired to disconnect the inner input shaft from the outer output shaft. Accordingly, this invention provides a releasable coupling slidably mounted on and drivingly connected to the output shaft for coupling the input shaft to the output shaft, the releasable coupling having a retaining pin. An annular cam is slidably mounted on the integrated drive generator frame radially outwardly of the output and input shafts and has inner ramped surfaces thereon for engaging the retaining pin, the retaining pin releasing the releasable coupling to thereby decouple the input shaft from the output shaft when the cam is activated by sliding movement to thereby provide shaft disconnect internally of the concentrically mounted input and output shafts.