Saudi Arabia is in the midst of redefining the vision for the country's future and creating an economy that is not dependent on fossil fuels. This work presents a pathway for Saudi Arabia to transition from the 2015 power structure to a 100% renewable energy based system by 2050 and analyse the benefits of integrating the power sector with the growing desalination sector. It is found that Saudi Arabia can transition to a 100% renewable energy power system by 2040 whilst meeting the growing water demand through seawater reverse osmosis (SWRO) desalination plants. The dominating renewable energy sources are PV single-axis tracking and wind power plants with 210 GW and 133 GW, respectively. The levelised cost of electricity (LCOE) of the 2040 system is 48 €/MWh. By 2050, PV single-axis tracking dominates the power sector due to the further reduction in the capital costs alongside cost reductions in supporting battery technology. This results in 80% share of solar PV in the total electricity generation. Battery storage is required to meet the total electricity demand and by 2050, accounts for 48% of the total electricity demand. The LCOE is estimated at 38 €/MWh, required capacity of PV single-axis tracking is 369 GW and wind power plants 75 GW. In the integrated scenario, due to flexibility provided by the SWRO plants, there is a reduced demand for battery storage and power-togas (PtG) plants. In addition, the ratio of the energy curtailed to the total energy generated is lower in all time periods from 2020 to 2050, in the integrated scenario. As a result, the annual levelised costs of the integrated scenario is found to be 2%-4% less than the non-integrated scenario.