Water-atmosphere flux of ammonia (NH₃) remains an uncertainty in the global NH₃ budget and quantification is fundamental for estimating nitrogen deposition loading and cycling in sensitive coastal ecosystems. This study quantifies monthly water-atmosphere NH₃ flux at 10 sites (nine estuary sites and one Gulf of Mexico site) spanning ~400 km of the Texas Coastal Bend from 9/2018 to 4/2019. The regional average NH₃ flux was 2.52 ± 3.57 ng m^-2 s^-1 denoting net NH₃ emission and the annual range among the 10 sites was -2.61 to 8.68 ng m^-2 s^-1.  This range falls within the range of the very limited number of reported water-atmosphere NH₃ fluxes in the open ocean and estuaries. Generally, NH₃ flux in fall months featured NH₃ emission from surface waters while winter featured NH₃ deposition and spring months varied between emission and deposition. Many physical and chemical factors (e.g. temperature, salinity, NH₄⁺ (aq), atmospheric NH₃, wind speed, pH) impact the direction and magnitude of NH₃ flux and principal component analysis is employed to provide insight to the significant influences on flux. The overall annual emission flux of 0.79 kg ha^-1 yr^-1 is ~18% of recently modeled total dry N deposition for the region (4.5 kg ha^-1 yr^-1). An approximate total of 0.33 Mg NH₃ is emitted from the nine estuaries per year, and although still dwarfed by agricultural emissions, this is ~4.6 and 1.2 times greater than National Emissions Inventory estimated emissions for electric generating units and on-road vehicles, respectively, in surrounding Texas Coastal Bend counties. As a potentially substantial contributor to NH₃ concentrations in local ambient air and emission/deposition pathway in sensitive coastal environments, the water-atmosphere flux of NH₃ requires comprehensive quantification across varying estuary systems to aid nitrogen loading estimates and guide NH₃ emission mitigation efforts.