Groundnut ringspot virus is a negative-sense single-stranded RNA virus that belongs to the genus Tospovirus and is the prevalent member of this genus in Brazil. This work presents the nucleotide sequence of the L RNA, with a single open reading frame of 2873 amino acids in the complementary strand corresponding to the RNA-dependent RNA polymerase (L protein), as well as the characterization of conserved domains of the L protein by in silico analysis. Phylogenetic analysis of different L protein domains confirmed that GRSV is a member of the American clade, and comparison with a N-protein indicates that phylogeny based on L protein sequences may be more reliable than that based on the N protein.