<p>We present a new and improved version (V4.0) of the NASA standard nitrogen dioxide (NO<sub>2</sub>) product from the Ozone Monitoring Instrument (OMI) on the Aura satellite. This version incorporates the most salient improvements for regional OMI NO<sub>2</sub> products suggested by expert users, and enhances the NO<sub>2</sub> data quality in several ways on a global scale through improvements to the air mass factors (AMFs) used in the retrieval algorithm. The algorithm is based on a conceptually new, geometry-dependent surface Lambertian equivalent reflectivity (GLER) operational product that is available on an OMI pixel basis. GLER is calculated using the vector linearized discrete ordinate radiative transfer (VLIDORT) model, which uses as input high resolution bidirectional reflectance distribution function (BRDF) information from NASA’s Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) instruments over land and the wind-dependent Cox–Munk wave-facet slope distribution over water, the latter with contribution from the water-leaving radiance. The GLER combined with consistently retrieved oxygen dimer (O<sub>2</sub>-O<sub>2</sub>) absorption-based cloud fractions and pressures provide high-quality data inputs to the new NO<sub>2</sub> AMF scheme. The new AMFs increase the retrieved tropospheric NO<sub>2</sub> by up to 50 % in highly polluted areas; these differences arise from both cloud and surface BRDF effects as well as biases between the new MODIS-based and previously used OMI-based climatological surface reflectance data sets. We quantitatively evaluate the new NO<sub>2</sub> product using independent observations from ground-based and airborne instruments. The improved NO<sub>2</sub> data record can be used for studies related to emissions and trends of nitrogen oxides (NO<sub>x</sub>) and co-emitted gases. The new V4.0 data and relevant explanatory documentation are publicly available from the NASA Goddard Earth Sciences Data and Information Services Center (<a href=" https://disc.gsfc.nasa.gov/datasets/OMNO2_V003/summary/"target="_blank">https://disc.gsfc.nasa.gov/datasets/OMNO2_V003/summary/</a>), and we encourage their use over previous versions of OMI NO2 products.</p>