The blacksail snake mackerel (Thyrsitoides marleyi), also known as the black snoek, is a species of snake mackerel found in the Indo-Pacific from shallow water to a depth of at least where they appear to prefer slopes on seamounts and ridges. They are known for making diel vertical migrations to near-surface waters at night, feeding on fish, squid and crustaceans. This species reaches a total length of though most are around . This species is of minor importance to local commercial fisheries.
T. marleyi is the only extant (living) member of the genus Thyrsitoides. However, two extinct species are also known: T. zarahoustrae <small>Arambourg, 1967</small> from the Late Eocene Pabdeh Formation of Iran and potentially the Early Oligocene of Romania, and T. cangrandei from the Early Eocene Chiusole Formation of Italy.