The chestnut-breasted mannikin (Lonchura castaneothorax), also known as the chestnut-breasted munia or bully bird (in Australia), is a small brown-backed munia with a black face and greyish crown and nape. It has a broad ferruginous breast bar above a white belly. The species is found in Australia, New Caledonia, Indonesia, and Papua New Guinea. This species has also been introduced to French Polynesia.