The Lagoon 55 Millenium is a 18.38-metre current production model in Lagoon's Sailing Catamarans range. Official specifications give a 9.00-metre beam and 1.55-metre draft.
Lagoon lists Twin 110 hp engines. Fuel capacity is 1,100 litres and water capacity is 960 litres. Published layouts provide up to 6 cabins. Lagoon publishes four-, five- and six-cabin versions; cabin_count records the maximum published layout.