Kōwhai (Māori pronunciation: [kɔːɸai] or [kɔːfai]) are small woody legume trees within the genus Sophora in the family Fabaceae that are native to New Zealand. There are eight species, with Sophora microphylla and S. tetraptera being the most recognised as large trees. Their natural habitat is beside streams and on the edges of forest, in lowland or mountain open areas. Kōwhai trees grow throughout the country and are a common feature in New Zealand gardens. Outside of New Zealand, kōwhai tend to be restricted to mild temperate maritime climates.

The blooms of the kōwhai are widely regarded as being New Zealand's unofficial national flower. As such, it is often incorporated as a visual shorthand for the country, such as in Meghan Markle's wedding veil which included distinctive flora representing all Commonwealth nations.

The Māori word kōwhai is related to other words in some Polynesian languages that refer to different species that look superficially similar such as Hawaiian: 'ōhai (Sesbania tomentosa), Tahitian: ofai (Sesbania grandiflora) and Marquesan kohai (Caesalpinia pulcherrima). Kōwhai is also the Māori word for the colour yellow. The spelling kowhai (without a macron) is common in New Zealand English.