Udea hyalistis is a moth in the Crambidae family. It was described by Lower in 1902. It is found in Australia, where it has been recorded from Victoria. The wingspan is 22-26 mm. The forewings are pale brownish-grey with a clear white median subcostal spot, edged with some darker scales. There is a similar spot narrower and twice constricted. The hindwings are ochreous-whitish with some brownish-grey irroration, an antemedian dot and a subterminal band of the same colour.