A new Brazilian Protoneurinae damselfly, Forcepsioneura lopii sp. nov. (holotype male deposited in DZUP: Brazil, São Paulo State, Cananéia, Ilha do Cardoso State Park) is described, and diagnosed based on two males and one female. This small dark yellow-orange Forcepsioneura Lencioni, 1999, inhabits typical restinga-like formations in southern Brazil. The coloration and short ventrobasal process of the male cercus of Forcepsioneura lopii sp. nov. make it similar to the larger montane species of the orange-black group, i.e., F. grossiorum Machado, 2005, F. itatiaiae (Santos, 1970), F. janeae Pimenta et al., 2019, F. lucia Machado, 2000, and F. serrabonita Pinto & Kompier, 2018. However it occurs in lowlands and the cercus is slender as in the light blue group, i.e., F. gabriela Pimenta et al., 2019, F. garrisoni Lencioni, 1999, F. haerteli Machado, 2001, F. regua Pinto & Kompier, 2018, and F. sancta (Hagen in Selys, 1860). The very acute, spur-like process on the mediobasal process of male cercus is unique. This is only one of several undescribed species recently discovered in Forcepsioneura, and it reaffirms the necessity for additional investigations to understand the richness and diversification of this genus.