This review presents a synthesis of literature published on deuterium and oxygen isotopes in groundwater collected from different aquifers in North Oman. The identification of the main hydrological processes which characterize the main aquifers in the North Oman was the main objective of several previous studies. The main focus was to identify zones and mechanisms of groundwater recharge to the different aquifers. Hajar Super group was identified as a main aquifer that receives recharge and transfer freshwater into neighboring aquifers namely ophiolite, alluvium, Hawasina and Tertiary aquifers. A mass balance was also applied in previous studies to groundwater alluvium aquifer and indicated that 2/3 of recharge occurs along the wadi channels and that 1/3 is from the subsurface. Recently it was estimated that 13–68% of groundwater in the ophiolite aquifer is coming from the HSG contrary to the previous estimates of 10%.