Sirius Passet, Paleontological site in Peary Land, Greenland.

Sirius Passet is a fossil site in the Buen Formation on the east shore of J.P. Koch Fjord in Peary Land, northern Greenland. Its dark grey and black rocks, about 518 million years old, hold flattened, segmented animals with spiny appendages, preserved as lighter grey or beige traces. The site comprises six places in Nansen Land.

A. Higgins of the Geological Survey of Greenland found sponge fossils at the site in 1984. Simon Conway Morris and others published a preliminary account in 1987, and expeditions led by J. S. Peel and Conway Morris returned from 1989 onward. A field collection of perhaps 10,000 fossil specimens has been amassed.

The name comes from the Sirius sledge patrol that operates in North Greenland. In October 2022 the International Union of Geological Sciences listed the 'Cambrian Explosion in Sirius Passet' among its 100 geological heritage sites, citing its reference value for the history of geological sciences.

The site lies at 82°47′ N on the east shore of J.P. Koch Fjord in Nansen Land, Peary Land, reachable only by air and then overland in the High Arctic. Fieldwork has been limited to about nine expeditions since 1984, mostly in summer. Access requires cold-weather gear and helicopter or ski-plane logistics; the terrain is rocky and the weather changes fast.

The fossils include Kerygmachela and Pambdelurion, two panarthropods that feature in debates about the origin of modern animal phyla. The site also yielded Halkieria, a problematic taxon, and many specimens lack eyes. The fossils lie in the Buen Formation and were named after the Sirius sledge patrol of North Greenland.