Vailuluʻu is a volcanic seamount discovered in 1975. It rises from the sea floor to a depth of 593 m (1,946 ft) and is located between Taʻu and Rose islands at the eastern end of the Samoa hotspot chain. The basaltic seamount is considered to mark the current location of the Samoa hotspot. The summit of Vailuluʻu contains a 2 km wide, 400 m deep oval-shaped caldera. Two principal rift zones extend east and west from the summit, parallel to the trend of the Samoan hotspot. A third less prominent rift extends southeast of the summit.

Eruptions at Vailuluʻu were recorded in 1973. An earthquake swarm in 1995 may have been related to an eruption from the seamount. Turbid water above the summit shows evidence of ongoing hydrothermal plume activity. Vailuluʻu may breach the surface of the ocean and officially become an island if a high rate of eruptions continue.

The seamount was first discovered in 1975 after seismic activity, including earthquakes, was noted in the area and was originally known as either Rockne Volcano or Faʻafafine seamount. The name Vailuluʻu refers to a sacred rain that supposedly fell with every gathering for the Tui Manuʻa, the paramount chief of the Manuʻa Islands. It was coined by the American Samoa student Taulealo Vaofusi, the winner of a naming competition, and assigned in 2000. The Nafanua cone is named after a Samoan war goddess, Nafanua. Today the seamount is part of the National Marine Sanctuary of American Samoa.

Vailuluʻu is located east of American Samoa; the easternmost island Taʻu is located 43 kilometres (27 mi) west of Vailuluʻu. Even farther west lie Ofu-Olosega and Muli, while Malumalu Seamount is located south of Ofu-Olosega. Rose Atoll and Malulu Seamount are located southeast from Vailuluʻu.

Vailuluʻu is a conical seamount and reaches a depth of 593 metres (1,946 ft) and features a 2 kilometres (1.2 mi) wide and 0.4 kilometres (0.25 mi) deep crater; the shallowest part of the seamount is located on the western crater rim which has a scalloped appearance. Two additional summits and three breaches can be found in the crater rim; the deepest breach lies in the southeast and is 795 metres (2,608 ft) deep.

The seamount has a star-like shape, with two prominent ridges east and west and a somewhat less prominent ridge south of the volcano; it also features smaller ridges at its foot and amphitheatre-shaped scars from landslides. The total volume of the volcano is estimated to be about 1,050 cubic kilometres (250 cu mi) and its height above the seafloor is comparable with that of major isolated volcanoes such as Fuji, although much smaller than compound volcanic islands such as Hawaii. The seafloor around Vailuluʻu lies at a depth of about 5 kilometres (3.1 mi); the foot of the seamount has a diameter of about 35 kilometres (22 mi). A saddle at a depth of 3,200 metres (10,500 ft) depth connects it to Taʻu.

A 300 metres (980 ft) high cone in the crater bears the name Nafanua, and formed in 2004 in the western half of the crater. Prior to the formation of the cone, the crater contained several pit craters; it is possible that the crater was once occupied by a higher cone, which might have risen to shallow depths. The Nafanua cone consists mostly of pillow lavas.

Hydrothermal vents are found at a number of sites within the crater with varied characteristics, including high and low temperature vents. The bulk of the venting occurs through the a complex known as the Northern Moat Hydrothermal Complex and reaches temperatures of 80 °C (176 °F), while another complex, called the South Wall Fe Chimney, vents water with temperatures of 20 °C (68 °F) in massive vents. The hydrothermal activity influences the waters within the crater, making them turbid and warmer than the water in the free ocean. Low temperature hydrothermal vents are found on the western ridge of Vailuluʻu as well.