<p>Owing to their nutritional and economic value, cephalopods are important marine resources for coastal communities around the world. To manage these resources and use them in a sustainable manner, it is essential to be able to accurately identify cephalopods. Despite the high commercial value of cephalopod fisheries in Vietnam, only a few taxonomic studies have been conducted on this class of molluscs in this country. In addition, the identification of cephalopods based on morphological features is challenging because of their soft-bodied nature, variable pigmentation-related traits, and morphological homology to closely related species. Against this background, DNA barcoding has recently been developed as a powerful tool for classifying marine invertebrates. The current study was conducted to identify cephalopods collected in the Gulf of Tonkin, Vietnam. In total, 41 cephalopod samples were collected and sequenced for part of the cytochrome c oxidase subunit 1 (COI) gene. Molecular analysis indicated that these 41 sequences belong to 14 species of cephalopods, including 4 squids (<i>Loliolus uyii</i>, <i>Sepioteuthis lessoniana</i>, <i>Uroteuthis chinensis</i>, and <i>U. duvaucelii</i>), 1 bobtail squid (<i>Euprymna berryi</i>), 4 cuttlefishes (<i>Sepia aculeata</i>, <i>Sepia pharaonis</i>, <i>Sepiella inermis</i>, and <i>Sepiella japonica</i>), and 5 octopuses (<i>Amphioctopus aegina</i>, <i>A. fangsiao</i>, <i>A. marginatus</i>, <i>A. neglectus</i>, and <i>Callistoctopus luteus</i>). In all of the examined species, intraspecific distances were lower than interspecific ones. However, there was high intraspecific distance in <i>Uroteuthis duvaucelii</i>, suggesting that this taxon might contain cryptic species. Consistent with the genetic distance analysis, the phylogenetic tree revealed distinct species for each group, with separate clades for <i>Uroteuthis duvaucelii</i> sequences. This study provides fundamental data to aid the management of cephalopod resources in Vietnam.</p>