Actinopus comprises 98 species of trapdoor spiders endemic to the Neotropic region. In southwestern Buenos Aires, Argentina, four species are recorded: Actinopus casuhati Ríos-tamayo & Goloboff, 2018, A. laventana Miglio, Pérez-Miles & Bonaldo, 2020, A. patagonia Ríos-tamayo & Goloboff, 2018, and A. puelche Ríos-tamayo & Goloboff, 2018; females of A. puelche are unknown. By the examination of Actinopus from Bahía Blanca district, southwestern Buenos Aires province, we found specimens that do not fit within any of the known species. Thus, we implemented an integrative approach combining molecular and morphological evidence to describe, diagnose and illustrate Actinopus obrerografico sp. nov. In addition, we describe for the first time the female of A. puelche. We also present new distributional records for A. patagonia and A. puelche. Males of A. obrerografico sp. nov. can be distinguished by having red tarsi and metatarsi, and bulb with well developed keels and apophysis, and no denticles along the inferior prolateral keel; females, can be distinguished by the spermathecae, bilobed with external lobe well developed and an internal basal proejection. Females of A. puelche can be distinguished by having a spermathecae with slight marked lobes. A first molecular phylogeny using Maximum likelihood yielded Actinopus as monophyletic, A. obrerografico sp. nov. as a distinct clade and A. puelche more related to the remaining Argentinean species despite living in sympatry with A. obrerografico sp. nov.
