The Mundo Novo tree frog, Hypsiboas marginatus, is a species of frog in the family Hylidae. It is endemic to southeastern Brazil where it is known from the easternmost Rio Grande do Sul and adjacent southeastern Santa Catarina. Its natural habitats are forested mountain slopes near streams with clear running water. The eggs are deposited on vegetation hanging into the water. It is a common species although habitat loss and water pollution are threats.