Asaphus (/ˈæsæfʌs/) is a genus of trilobites that is known from the Lower (upper Arenig) and Middle Ordovician of northwestern Europe (Sweden, Estonia, Saint Petersburg Area).

The headshield (or cephalon) and tailshield (or pygidium) are semicircular and without a border (defined by a furrow or a change in convexity parallel to its margin).

It may have faint lateral glabellar furrows or be smooth, and sometimes an inconspicuous tubercle is present just in front of the hardly discernible occipital ring.

The natural fracture lines (sutures) of the head run along the top edges of the compound eye.

The lateral corners of the palate (or hypostome), visual from the ventral side, are more or less protruding, and the posterior part is forked with two triangular teeth.