Guaiacum sanctum, commonly known as Holywood or Holywood Lignum-vitae, is a species of flowering plant in the creosote bush family, Zygophyllaceae. It ranges from southern Florida in the United States and the Bahamas south to Central America and the Greater Antilles. It is threatened by habitat loss.

This tree is one of two species which yield the valuable Lignum vitae wood, the other being Guaiacum officinale. This small tree is slow growing, reaching about 7 m (23 ft) in height with a trunk diameter of 50 cm (20 in). The tree is essentially evergreen throughout most of its native range. The leaves are compound, 2.5–3 cm (0.98–1.2 in) in length, and 2 cm (0.79 in) wide. The purplish blue flowers have five petals each, and yield yellow pods containing black seeds encapsulated separately in a red skin.

Guaiacum sanctum is the national tree of the Bahamas.

Holywood lignum vitae (Guaiacum sanctum) is a stunning tree which produces beautiful blue flowers, either solitarily or in clusters. These flowers have five petals and usually measure just over a centimetre across.

The leaves of the holywood lignum vitae comprise of three to five pairs of dark green leaflets, which measure about three centimetres in length and have a small point at the tip. During the hottest part of the day, the leaflet pairs may sometimes fold together. The fruits of this species have four or five lobes and are bright orange-yellow when mature. They open to expose red, fleshy arils (seed coverings) which contain the hard, black, rounded seeds. The seeds of the holywood lignum vitae measure about one centimetre in length.

The holywood lignum vitae generally grows as a relatively low tree with a gnarled truck and a spreading, rounded crown of drooping branches. Its wood is notable for its unique greenish-brown colour. The wood is strong and dense, and sinks when placed in water.