A new large treefrog species of the genus Hyla is described from São José da Vitória and Wenceslau Guimarães, in southern State of Bahia, Brazil. Hyla exastis sp.nov., morphologically belonging to the H. boans (Linnaeus, 1758) species group and related to H. pardalis Spix, 1827 and H. lundii Burmeister, 1856, is characterized by: large size (snout-vent length, 81.1-99.0mm in males, 86.5mm in female); dorsum granulose; a developed crenulate fringe along external border of forearm, finger IV, foot, and toe V; calcar appendix conspicuous; anal plate distinct, inferiorly delimited by a transversal row of white tubercles; dorsum grayish yellow (in life) or brown (in preservative), with dark brown to black marks without forming a definite pattern, resembling tree bark with lichens; in life, palm of hand bluish yellow, fingers and disks deep blue, and webbing yellowish gray; sole of foot gray, toes and disks deep blue, and webbing black; palmar formula, I2-2+ II1-2- III11⁄2-1IV;plantarformula,I1-1II1-11⁄2III1-11⁄2IV11⁄2-1V.
