The Lassus Mountains are a large group of mountains, 15 nautical miles (28 km) long and 3 nautical miles (6 km) wide, rising to 2,100 metres (6,900 ft) and extending south from Palestrina Glacier in the northwest part of Alexander Island, Antarctica. They overlook Lazarev Bay and a few minor islands within the bay such as Dint Island and Umber Island; Haydn Inlet lies to the south while the Havre Mountains lie immediately north.