Abstract During the SokhoBio expedition in 2015, deep-sea benthic invertebrate fauna of the Kuril Basin of the Sea of Okhotsk and the Pacific Ocean between the Bussol Strait and the Kuril-Kamchatka Trench was sampled on board of the R/V Akademik M.A. Lavrentyev. Over 18,400 polychaetes belonging to 48 families, 139 genera, and 189 species were found in the studied area. The abyssal zone of the Sea of Okhotsk and the Pacific slope of the Kuril-Kamchatka Trench are the areas of high polychaete diversity and species richness. The diversity of the Kuril Basin is higher than that in the deep-sea basin of the Sea of Japan and is comparable to that in the abyssal plain adjacent to Kuril-Kamchatka Trench. A total of 160 polychaete species belonging to 124 genera and 47 families were identified from depths of 1676–3366 m in the Kuril Basin. Over half of these (93 species, 58%) occur on the Pacific slope of the Kuril-Kamchatka Trench. The records of widespread and eurybathic species common to both the Kuril Basin and the Pacific slope confirm the relationship between the abyssal fauna of the Kuril Basin and deep sea North-West Pacific. Nine genera and 18 species have been reported for the North-West Pacific for the first time. One family, 36 genera and 49 species were first records for the Sea of Okhotsk. More than 40% of the collected polychaete species were new to science. Among these, a sigalionid Labioleanira okhotica sp. nov. described herein, is the deepest (3211–4803 m) record for the genus Labioleanira. This species is easily recognized by the lack of eyes, the presence of nodular auricles instead of ear-shaped ones, and the presence of small dorsal tubercles on chaetiger 3. The genus Labioleanira Pettibone, 1992 is newly recorded in the North-West Pacific. An updated key to the species of the genus Labioleanira is provided.