<span>Understanding ocean physical connectivity is essential for characterizing and predicting transport patterns, which in turn play a fundamental role in several marine processes. Here, we present an analysis of 30 years of surface water connectivity for the Bay of Biscay, derived from backward Lagrangian particle simulations driven by hourly high-resolution surface velocity reanalysis fields. The Lagrangian simulations are used to characterize transport pathways within and between key subregions across integration times of 7, 30, and 90 days, thereby capturing connectivity from weekly to seasonal scales.</span> </p> <p><span>Results show that the obtained seasonal cycle of connectivity reflects the seasonal variability of regional ocean circulation: i) The northward transport along the shelf by the Iberian–Poleward Current, ii) the presence of transport barriers along the continental slope, and iii) the enhanced cross-shelf transport from the Spanish shelf during spring and from the French shelf during summer. Regional maps of particle origins and transit times reveal areas of strong isolation along the French coast and zones of intensive mixing at the French Spanish border. While interannual variability is evident, the simulations also indicate a slight but significant long-term decrease in transport from the Spanish to the French shelf.</span> </p> <p><span>Overall, these results provide an overview of the main pathways of transport and retention within the Bay of Biscay at different time scales, offering insights into its potential role in different key ocean processes such as marine litter or plankton dispersal, genetic exchange, and ecosystem functioning.</span>