Arachnanthus sarsi is a species of tube-dwelling anemone in the family Arachnactidae.

This species is found in the North Atlantic in subtidal sand or muddy sand at depths of 15–130 m. This is a large sea anemone, with a diameter of up to 20 cm (8 in) when fully expanded and a height of a similar amount.

There are two whorls of tentacles, the outer ring of about thirty are long and slender, while the inner ring, consisting of a similar number, are short and are extended upward, turning inward at the tip to form a cone; it is this feature which distinguishes this species from the otherwise similar Cerianthus lloydii.

It occurs in the north-east Atlantic Ocean off Scotland and Ireland.

[4][5] In Northern Ireland it is known only from the southern half of Rathlin Island.