Nishikubiki (西頸城郡 Nishikubiki-gun?) was a district located in Niigata Prefecture, Japan.
The district was founded in 1878, when the former Kubiki District split into Higashikubiki District, Nakakubiki District, and Nishikubiki District. At the time of founding, the district covered the city of Itoigawa and the Nadachi section of the city of Jōetsu. The district seat was located at the town of Itoigawa (now the city of Itoigawa).
As of 2003, the district has an estimated population of 23,292 and a density of 67.40 persons per km². The total area is 345.56 km².