Cassiopea (P 401) is the lead ship of a class of four heavy patrol ships built for the Italian Navy in 1987. The Cassiopea-class were designed to replace the Albatros-class corvettes as simple, cost-efficient patrol vessels for offshore fishery patrol; each ship is armed with a single 76 mm OTO-Melara M.M.I. autocannon derived from the recently scrapped Bergamini-class frigates to save costs.

As for Cassiopea, she was laid down on 18 March 1987 at the Fincantieri shipyard in Muggiano, launched on 19 July 1988, and commissioned on 21 October 1989. From 2013 to 2014, Cassiopea took part in Operation Mare Nostrum to rescue migrants on dangerous Mediterranean Sea crossings, including the major shipwreck near Lampedusa Island on 3 October 2013. While Cassiopea's sister ship Libra (P 133) was sold to the Albanian Naval Force on 5 April 2025, the remaining three ships, including Cassiopea, have served with the Italian Navy to this day.

Cassiopea was introduced in Update 2.53 "Line of Contact". Armed with a 76 mm OTO-Melara M.M.I. autocannon with a slightly lower but still fast rate of fire compared to the one found on the Sparviero, Cassiopea is capable of damaging early destroyers or overwhelming smaller coastal vessels. With access to HE-VT shells and an air search-and-tracking radar, Cassiopea can also pose a threat to enemy aircraft. However, despite having a detailed damage model, Cassiopea suffers from a very low crew count of 60, all of whom can be easily eliminated by destroyer-calibre HE rounds due to their compartments being located on an unarmoured deck of the ship.