Hello and welcome to just answer Jeep. It could be a few things. 1, your oil pressure sending unit has failed and sending the wrong voltage signal to the gauge, 2 the wiring between the sending unit and the gauge is shorted to ground, or 3 you actually have an oil pressure that is too high. Do this: disconnect the oil pressure sending unit connector at the sender. If the oil pressure reading is now at 0, then that eliminates the wiring shorted issue. If it stays high, then suspect a short (or maybe a gauge problem). If it does drop, then connect an actual oil pressure test gauge to the fitting where the oil pressure sending unit connects and read the actual pressure. It should be around 10 psi at idle, and around 40 at higher rpms. If it is higher than that then you may have a stuck pressure relief valve in the oil pump. This would mean replacement of the oil pump itself. If the pressure is normal, then replace the sending unit. The failed sending unit is the most common cause of this type of problem.
Hope this information helps. Let me know if you need more assistance with this.