Prehistoric tsunamis
Prehistoric tsunamis are tsunamis and so-called "megatsunamis" that occurred before recorded history. The events have been identified through oral tradition and/or geological evidence. Those events that have been identified through contemporary records are listed as historic tsunamis.
List
| Approx. date | Location | Cause | Evidence for tsunami |
| 66 million years BP | Chicxulub crater, Yucatan | asteroid strike | presumed |
| 35.5 million years BP | Chesapeake Bay | bolide impact | presumed |
| 10,000 yrs BP | Seton Portage, British Columbia | landslide into lake | presumed |
| 8,000 years BP | Mount Etna, Sicily | volcanic landslide | submarine sediments off Etna, submerged settlements off eastern Mediterranean coast, e.g. Atlit Yam |
| 8,000 years BP | Norwegian Sea | submarine landslip | deposited sediments in Scotland |
| 5,500 BP | Northern Isles | tsunami | deposits and contemporaneous mass burials |
| 4,000 BP | Réunion island | landslide | presumed |