Elachista watti is a moth in the Elachistidae family. It was described by Philpott in 1924. It is found in New Zealand. The wingspan is 7-8.5 mm. The forewings are metallic white with a linear spot of fuscous below the fold at three-fifths and a median fuscous streak from three-fourths to near the apex. The hindwings are greyish-fuscous.