Stigmella watti is a species of moth in the family Nepticulidae. This species was first described in 1989 by Hans Donner and Christopher Wilkinson. It is endemic to New Zealand and has been observed in Fiordland, Southland and on Stewart Island. The larvae feed on Olearia colensoi νar. grandis (now known as Macrolearia lyallii) and possibly Olearia oporina by mining the leaves of those plants. Larvae have been observed in May while adults are on the wing in February. S. watti was named in honour of Morris N. Watt.

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