Sophora microphylla, commonly known as weeping kōwhai and small-leaved kōwhai, is a species of flowering tree in the family Fabaceae native to New Zealand. It is the most widespread of the eight species of kōwhai (the New Zealand Sophora). It is also called South Island kōwhai, although this name is misleading as it is widely distributed throughout the main islands of the country.

Growing to 8 m (26 ft) tall and broad, it is an evergreen shrub or small tree. Each leaf is 10 cm (4 in) long with up to 40 pairs of shiny oval leaflets. It produces many racemes of pea-like yellow flowers from August or as early as May through to October. The specific epithet microphylla means "small-leaved". The plant has smaller leaflets (around 3–6 mm long by 2–5 mm wide) and flowers (1.8-5.0 cm long) than the other well known species, Sophora tetraptera (large-leaved kōwhai). When young S. microphylla has a divaricating and bushy growth habit with many interlacing branches, which begins to disappear as the tree ages.

It occurs throughout the main islands of New Zealand, though is scarce in parts of Northland and parts of the eastern North Island from East Cape south to northern Wairarapa.

The cultivar Sun King 'Hilsop' has gained the Royal Horticultural Society's Award of Garden Merit.

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