| Named By: | Luo, et al 1999 |
| Time Period: | 535-520 Ma |
| Location: | China, Qiongzhusi Formation |
| Size: | 2.5 centimeters |
| Diet: | unavailable |
| Fossil(s): | One preserved specimen |
| Classification: | | Chordata | Craniata | Agnatha | |
Haikouichthys is an extinct genus of craniate (animals with notochords and distinct heads) believed to have lived 525 million years ago, during the Cambrian explosion of multicellular life. Haikouichthys had a defined skull and other characteristics that have led paleontologists to label it a true craniate, and even to be popularly characterized as one of the earliest fishes. Cladistic analysis indicates that the animal is probably a basal chordate or a basal craniate; but it does not possess sufficient features to be included uncontroversially even in either stem group.