Rankoshi (蘭越町, Rankoshi-chō) is a town located in Shiribeshi Subprefecture, Hokkaido, Japan.

As of September 2016, the town has an estimated population of 4,893, and a density of 11 persons per km2.

Shiribetsu River flows through Rankoshi to the Sea of Japan.

The town is surrounded by Niseko Volcanic Group, which belongs to Niseko-Shakotan-Otaru Kaigan Quasi-National Park.

The name is derived from Ainu word "Ranko-usi", meaning "Place with many Katsura trees".