is a town located in Tokachi Subprefecture, Hokkaidà Â, Japan. , the town had an estimated population of 5,742 in 3111 households, and a population density of 10 people per km<sup>2</sup>. The total area of the town is . Hiroo is recognized as the only place in Japan to be designated as a "Santa-Land" from the municipal government of Oslo, Norway.
Hiroo is located in southern Hokkaido in the southernmost part of the Tokachi Subprefecture. The western part is mountainous and originates from the Hidaka Mountains, and is part of the Hidakasanmyaku-Erimo-Tokachi National Park. The eastern part borders the Pacific Ocean.
Although cold for its latitude and coastal position, the humid continental climate (Köppen Dfb) of Hiroo is moderated by East Asian standards. Summers are cooled by the ocean and cloudy weather, whereas the influence of the Siberian landmass drops temperatures in winter. Due to the ice-free nature of the ocean, Hiroo stays narrowly above freezing during days, whereas nights regularly drop beneath .
Per Japanese census data, the population of Hiroo has declined in recent decades.
The area flourished from the Jomon period. A settlement of Ainu people existed along the southeast Hiroo River. It was part of Matsumae Domain in the Edo period and was on a road opened by the Tokugawa shogunate along the coast to Kushiro. It was the site of a jin'ya established to govern the entire Tokachi Province. During the Bakumatsu period in 1858, it was awarded to Sendai Domain, which relocated farmers, carpenters, and woodsmen to the area and began cultivating grain and vegetables. In 1906, the village of Moyori was established under the second-class town and village system. Its name was changed to Hiroo Village in 1926, and was elevated to town status in 1946.
The 2011 Tohoku earthquake and tsunami resulted in a 2.8m tsunami striking Hiroo, causing over 1 billion yen in damage.
Hiroo has a mayor-council form of government with a directly elected mayor and a unicameral town council of 13 members. Hiroo, as part of Tokachi Subprefecture, contributes four members to the Hokkaidà  Prefectural Assembly. In terms of national politics, the town is part of the Hokkaidà  11th district of the lower house of the Diet of Japan.
The main economic activities of Hiroo are commercial fishing, agriculture (field crops), and dairy farming. Tokachi Port (a nationally important port) is located here.
Hiroo has two public elementary schools and one public middle school operated by the town. The town has one public high school operated by the Hokkaido Board of Education.
Hiroo has not had any passenger railway services since the closure of the JR Hokkaido Hiroo Line in February 1987. The closest railway stations are Obihiro Station and Samani Station, each of which are two hours away by car or bus.
Hiroo's mascots are and .