The Quad-Polarization Oil Spill Detection (QPOSD) dataset contains 41 fully polarimetric L-band scenes acquired over the U.S. Gulf of Mexico between 2010 and 2022. Each scene includes quad-polarization SAR measurements (HH, HV, VH, VV) and pixel-level semantic segmentation masks for sea surface, oil spill, look-alike phenomena, and land. The dataset supports reproducible research and benchmarking of SAR-based oil spill detection and segmentation methods. Keep in mind that the images are already normalised so no need to use batch normalisation again.