Abstract
We present novelties in Thismiaceae for the south of the Brazilian Amazon, resulting from botanical expeditions in the north of the Mato Grosso State. The occurrence of four species is recorded: Thismia hyalina; T. melanomitra; T. singeri and a species new to science: T. ribeiroi. These are the first records of the family Thismiaceae, as well as of the genus Thismia and these species for the Mato Grosso State. Thismia melanomitra is a new species for the flora of Brazil and T. singeri is the second record of the species for Brazil. In this study, we also describe and illustrate the new species Thismia ribeiroi.