The Silver Shell for Best Supporting Performance (Spanish: Concha de plata a la mejor interpretación de reparto; Basque: Taldeko interpretazio onenaren zilarrezko maskorra) is one of the main awards presented at the San Sebastián International Film Festival to the Best Supporting Performance of a competing film. In 2021, the San Sebastián International Film Festival announced that the two acting categories would be retired, and replaced with one gender-neutral category, with both Best Actor and Best Actress merging into the Best Leading Performance and Best Supporting Performance category.