| Named By: | Briggs & Collins in 1988 |
| Time Period: | Middle Cambrian |
| Location: | Canada, British Columbia - Burgess Shale |
| Size: | Individuals measure between 46 and 93 millimetres long |
| Diet: | Carnivore |
| Fossil(s): | At least 5 individual specimens |
| Classification: | | Arthropoda | Chelicerata | |
Sanctacaris is a Middle Cambrian arthropod from the Burgess Shale of British Columbia. It was most famously regarded as a primitive chelicerate, a group which includes spiders and scorpions, although subsequent phylogenetic studies have not always supported this conclusion; it is best accommodated in the arachnate clade (i.e. as a stem-group chelicerate).
Sanctacaris specimens range from 46 to 93 mm in length. The head bears five pairs of grasping appendages and a sixth pair of large separate appendages. The grasping appendages each bear a short antenna-like second appendage. There are 11 body segments, each with a pair of walking legs and gills. There is a broad, flat paddle-like telson.
Originally Sanctacaris was called informally 'Santa Claws'. Its Latin name translates as "saintly crab". Unlike most other Burgess forms, Sanctacaris is not present in Charles Walcott's 1909 quarry and was discovered at a different level by Desmond Collins in 1980-1981.