A riser disconnect/reconnect system having a disconnection package (RDP) and a modified lower marine riser package (LMRP) are provided for quick disconnection of the marine drilling riser (MDR) from the LMRP to facilitate access to the LMRP or BOP stack. The RDP includes a flex joint and a hydraulically-actuated release connector (RC) with a connecting mandrel that engages a modified LMRP. In an emergency, the RDP is disconnected from the LMRP allowing access to the BOP stack for intervention. The RDP may be disconnected from the LMRP for recovery of the LMRP or BOP stack to the surface for repair or maintenance without recovering the MDR. The RC joins the flex joint to the uppermost annular blowout preventer in the LMRP. The release connector can be used in a standard or inverted position. Also provided are structural cages with complementary stab plates allowing access to various bypass ports and controls.