Phormium tenax (called flax in New Zealand English; harakeke in Māori; New Zealand flax outside New Zealand; and New Zealand hemp in historical nautical contexts) is an evergreen perennial plant native to New Zealand and Norfolk Island that is an important fibre plant and a popular ornamental plant. The plant grows as a clump of long, straplike leaves, up to two metres long, from which arises a much taller flowering shoot, with dramatic yellow or red flowers.

The fibre has been widely used since the arrival of Māori to New Zealand, originally in Māori traditional textiles and also in rope and sail making after the arrival of Europeans until at least WWII. It is an invasive species in some of the Pacific islands and in Australia.

The blades of the plant contain cucurbitacins, which are poisonous to some animals, and some of them are among the bitterest tastes to humans.