| Named By: | Joseph Leidy in 1870 |
| Time Period: | Albian-Maastrichtian[1] |
| Location: | USA, Alabama, Georgia, Kansas. Europe. Australia. Canada |
| Size: | 4 to 6 meters long |
| Diet: | unavailable |
| Fossil(s): | Many specimens from across the globe |
| Classification: | | Chordata | Actinopterygii | Osteoglossomorpha | Ichthyodectiformes | Ichthyodectidae | Ichthyodectinae | |
Xiphactinus (from Latin and Greek for "sword-ray") is an extinct genus of large (4.5 to 6 metre; 15 to 20 feet long) predatory marine bony fish that lived during the Late Cretaceous. When alive, the fish would have resembled a gargantuan, fanged tarpon (to which it was, however, not related). The species Portheus molossus described by Cope is a junior synonym of X. audax. Skeletal remains of Xiphactinus have come from Kansas (where the first Xiphactinus fossil was discovered during the 1850s), and Cretaceous formations all over the East Coast (most notably Georgia, Alabama, North Carolina, and New Jersey) in the United States, as well as Europe, Australia, Canada and Venezuela.