Scaeurgus unicirrhus is a benthic deep-sea octopus belonging to the family Octopodidae. It is widely distributed throughout the Mediterranean Sea and the eastern Atlantic Ocean, living between 30 and 600 m of depth. This species is known for its cryptic lifestyle, benthic habits, and morphological adaptations to deep-sea environments. It plays an important ecological role in continental slope ecosystems and has also been recorded around oceanic islands such as the Azores and Madeira.

Morphology S. unicirrhus has an oval, muscular body with a mantle length reaching up to 12 cm and arms extending to about 40 cm. The skin shows irregular papillae that provide camouflage on sandy or rocky bottoms. A distinctive characteristic is the single cirrus above each eye-hence the name "unicirrhus". Members of this genus possess two rows of suckers, a skin keel around the body margin, and males have the hectocotylus on the third left arm, unlike most other octopus species where the modified arm is the third right. According to Norman (2000), the species is typically reddish-brown, with robust arms and a tendency to inhabit soft substrates.

Taxonomy The genus Scaeurgus was described by Alcide d'Orbigny in 1840, who designated S. unicirrhus as its type species.