Marrella splendens is an arthropod known from the middle Cambrian Burgess Shale of British  Columbia. It is the most common animal in the Burgess Shale.

 Marrella itself is a small animal, 2 cm or less in length. The head shield has two pairs of long rearward spikes. On the underside of the head are two pairs of antennae, one long and sweeping, the second shorter and stouter. Marrella has a body composed of 24–26 body segments, each with a pair of branched appendages. The lower branch of each appendage is a leg for walking, while the upper branch is a long, feathery gill. There is a tiny, button-like telson at the end of the thorax. It is unclear how the unmineralized head and spines were stiffened. Marrella has too many antennae, too few cephalic legs, and too few segments per leg to be a trilobite. It lacks the three pairs of legs behind the mouth that are characteristic of crustacea. The legs are also quite different from those of crustaceans. The identification of a diffraction grating pattern on well-preserved Marrella specimens proves that it would have harboured an iridescent sheen—and thus would have appeared colourful. A dark stain is often present at the rear of the organism, probably representing decay fluids.

 Marrella is thought to have been a benthic (bottom-dwelling) marine scavenger living on detrital and particulate material. One exceptional specimen shows the organism fossilized in the act of moulting.

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