A new species of the genus <i>Atelopus</i>, <i>Atelopus fronterizo</i> <b>sp. nov.</b> , from eastern Panama is described herein based on molecular, morphological, and bioacoustic evidence. The new species can be distinguished from its congeners occurring in the region by a combination of the following characters: (1) phalangeal reduction in thumb; (2) SVL (females only) (35.1–50.1; <i>n</i>=13), HW/SVL (0.23–0.34; <i>n</i>=59), EYND/HW (0.27–0.39; <i>n</i>=60), TIBL/SVL (0.41–0.56; <i>n</i>=58), and HAL/SVL (0.22–0.28; <i>n</i>=49); (3) dorsal color pattern with green or yellow background and extensive dark olive blotches forming transversal bands or mottling; (4) advertisement call duration 176–235 ms with 19–34 pulses, average pulse rate 131.69 pulses/s, and dominant frequency 2 422.50–2 606.50 Hz. The new species is nested within the Central American clade of <i>Atelopus</i>. The minimum Kimura‐2‐parameter (K2P) genetic divergence between <i>Atelopus fronterizo</i> <b>sp. nov.</b> and its most phylogenetically similar congeners (<i>A</i>. <i>certus</i> and <i>A</i>. <i>glyphus</i>) is >2.6% for 16S and >4.9% for <i>COI</i> (<xref ref-type="table" rid="Table1">Table 1</xref>). The phylogenetic relationship is strongly supported by ultrafast bootstrap values for the maximum-likelihood trees of both genetic markers (16S, 96; <i>COI</i>, 100, <xref ref-type="fig" rid="Figure1">Figure 1A</xref>). Bayesian analysis of the concatenated sequences resulted in a tree with similar topology and high posterior probability support (0.99; Supplementary Figure S1). In addition, haplotype networks inferred from <i>COI</i> and 16S (Supplementary Figure S2) showed a well-separated clade containing the new species (two for <i>COI</i>, four for 16S). The number of mutational steps between haplotypes for the new species samples is very low (1–4 in 16S; one in <i>COI</i>), and the minimum number of mutational steps from the nearest species is nine for 16S (distance to <i>A</i>. <i>certus</i>) and 28 for <i>COI</i> (distance to <i>A</i>. <i>glyphus</i>).
