The grey warbler (Gerygone igata), also known by its Māori name riroriro or outside New Zealand as the grey gerygone, is an insectivorous bird in the family Acanthizidae endemic to New Zealand. Its natural habitat is temperate forests. It is sometimes known as the teetotum or rainbird.
One of the smallest birds found in New Zealand, grey warblers are about 11 cm long, with a weight of up to 6.5 g. It has grey-brown plumage (with a slight olive-green tint), with the face, throat and breast being pale-grey. The abdomen is off-white with a slight yellow tinge. The tail is white underneath and dark brown on top with white tips being visible in flight. They also have a distinctive ruby-red eye. Females are typically smaller than the male, but otherwise there is little sexual dimorphism. The young are paler with no hint of yellow and have brown eyes.
The male's song often starts with a series of three squeaks and builds into a distinctive long plaintive wavering trill that rises and falls. They sing throughout the year but most vigorously when nesting, during spring. Grey warblers are often heard more than they are seen.