This study investigates the use of contact spectroradiometry for the discrimination of grapevine varieties cultivated in the Rio Grande do Sul region, Brazil, focusing on Vitis vinifera and Vitis labrusca. Spectral data were collected from 574 leaf samples using a FieldSpec® 3 ASD spectroradiometer. Analytical methods included spectral ratio computation, first derivative analysis, standard deviation-based variability assessment, and Linear Discriminant Analysis (LDA) with Forward Stepwise variable selection. The results revealed that the most relevant spectral regions for varietal discrimination are concentrated in the visible and near-infrared (green and red-edge) and shortwave infrared (SWIR) ranges, reflecting leaf biochemical and structural properties. A set of ten key wavelengths achieved high classification performance, with the final LDA model reaching an average accuracy of approximately 93%. These findings highlight the potential of contact spectroradiometry as a tool for varietal mapping, traceability, and supporting certification of origin in viticulture.