By 2050, freshwater production by desalination plants is projected to increase more than sixfold compared to today's levels. Hundreds of seawater desalination plants currently operate in the Arabian Gulf, and the regional and local responses to brine discharge can be significant, especially on the Arabian coast in the southwestern Gulf. Here, we use a 2.5 km-resolution ocean model of the Gulf and the Sea of Oman to investigate the impact of increased salinity on circulation and water mass transformation within the Gulf under desalination forcing scenarios ranging from no desalination to an extreme 50-times present levels (50×). As forcing intensifies, salty, warm, dense waters sink to the bottom of the Gulf, leading to increases in salinity and temperature, with the most extreme scenario showing subsurface temperature and salinity near the southern shoreline rising by approximately 0.6 °C and 2 g/kg, respectively. With increasing forcing, we find stronger surface inflow of fresher water through the Strait of Hormuz and stronger outflow of warm, salty water into the Sea of Oman. The efficient exchange of water between the interior Gulf and the Sea of Oman, enhanced by brine discharge, strengthens and deepens through the Strait of Hormuz, increasing inflow and outflow rates by 20 % and effectively muting large-scale changes in temperature and salinity, even under extreme desalination scenarios. Impacts are much larger near desalination plants, with altered surface and subsurface flow patterns, increased mass transformation, and strengthened meridional and zonal overturning circulation.