Nikkō (日光市, Nikkō-shi, IPA: ) is a city in Tochigi Prefecture, Japan.  As of 2 December 2020, the city had a population of 80,239, in 36,531 households. The population density was 55 persons per km2. The total area of the city is 1,449.83 square kilometres (559.78 sq mi). 
 Nikkō is a popular destination for Japanese and international tourists. Attractions include the mausoleum of shōgun Tokugawa Ieyasu at the Nikkō Tōshō-gū shrine, and that of his grandson Iemitsu (Iemitsu-byō Taiyū-in), and the Futarasan Shrine, which dates to the year 767 AD. There are many famous hot springs (onsen) in the area. Elevations range from 200 to 2,000 meters. 
 The Japanese saying 【日光を見ずして結構と言うなかれ】 "Never say 'kekkō' until you've seen Nikkō"—kekkō meaning beautiful, magnificent or "I am satisfied"—is a reflection of the beauty and sites in Nikkō.
 Nikkō covers a vast area (1,449.83 km2) of rural northwestern Tochigi, approximately 140 km north of Tokyo and 35 km west of Utsunomiya, the capital of Tochigi Prefecture. It is the third-largest city (by area) in Japan, behind Takayama and Hamamatsu.
 Both the Watarase River and the Kinugawa River pass through the city. Lake Chūzenji and the Kegon Falls lie in Nikkō, as does the Nikko Botanical Garden. The city's many mountains and waterfalls have made it an important source of hydroelectric power. The area has been used for mining copper, aluminum and concrete.
 The weather in Nikkō is fairly similar to that of the northern island of Hokkaidō, even though Nikkō is much closer to Tokyo than Hokkaidō. The elevation of Nikkō plays an important role in this fact. It will usually get cooler as one ascends the mountain. The average temperature of Nikkō is around 7 °C (44 °F) with the warmest months reaching only about 22 °C (72 °F) and the coldest reaching down to about −8 °C (17 °F).
 Tochigi Prefecture
 Gunma Prefecture
 Fukushima Prefecture
 Nikkō has a Humid continental climate (Köppen Dfb). It has warm summers, and cold winters with heavy snowfall.  The average annual temperature in Nikkō is 7.2 °C (45 °F). The average annual rainfall is 2,202 millimetres (87 in). September is the wettest month. The temperatures are highest on average in August, at around 18.8 °C (66 °F), and lowest in January, at around −3.9 °C (25 °F).
 The highest temperature ever recorded in Nikkō was 30.8 °C (87.4 °F) on 8 August 2018. The coldest temperature ever recorded was −18.7 °C (−1.7 °F) on 15 March 1984.
 Per Japanese census data, the population of Nikkō has declined over the past 20 years.
 Shōdō Shōnin (勝道上人) established the temple of Rinnō-ji in 766, followed by the temple of Chūzen-ji [ja] in 784. The village of Nikkō developed around these temples. The shrine of Nikkō Tōshō-gū was completed in 1617 and became a major draw of visitors to the area during the Edo period. It is known as the burial place of the shōgun Tokugawa Ieyasu. A number of new roads were built during this time to provide easier access to Nikkō from surrounding regions. Nikkō Tōshō-gū, Futarasan Shrine, and Rinnō-ji now form the UNESCO World Heritage Site Shrines and Temples of Nikkō.
 During the Meiji period, Nikkō developed as a mountain resort, and became particularly popular among foreign visitors to Japan. The Japanese National Railways began service to Nikkō in 1890 with the Nikkō Line, followed by Tobu Railway in 1929 with its Nikkō Line.
 Nikkō was incorporated as a town in 1889, part of Kamitsuga District, with the establishment of the modern municipalities system. It was upgraded to city status in 1954 after merging with the neighboring village of Okorogawa.
 In March 2006, Nikkō absorbed the neighboring city of Imaichi, the town of Ashio from Kamitsuga District, the town of Fujihara, and the village of Kuriyama, both from Shioya District, to create what is officially the new and expanded city of Nikkō. The new city hall is located at the former Imaichi City Hall. The former Nikkō City Hall is now known as Nikkō City Hall-Nikkō Satellite Office.
 Nikkō has a mayor-council form of government with a directly elected mayor and a unicameral city legislature of 24 members. Nikkō contributes two members to the Tochigi Prefectural Assembly. In terms of national politics, the town is part of Tochigi 2nd district of the lower house of the Diet of Japan.
 Nikkō is heavily dependent on tourism to its historical and scenic sites and hot spring resorts. Hydroelectric power production, food processing, and the non-ferrous metals industry are also important components of the economy.
 Nikkō has been recognized by Japan's Office for the Promotion of Regional Revitalization (Kishida Cabinet Secretariat), which promotes the development of new technologies to combat depopulation, for its "high standard" of digital transformation/telework infrastructure. Related projects have been awarded over ¥19.1M in government grants.
 Nikko has 23 public primary schools, 12 public middle schools and three combined public primary/midde schools operated by the city government. The city has three public high schools operated by the Tochigi Prefectural Board of Education. The prefecture also operates one special education school for the handicapped.
 High schools:
  JR East –  Nikkō Line 
  Tōbu Railway – Tōbu Nikkō Line
  Tōbu Railway – Tōbu Kinugawa Line
 Yagan Railway
 Watarase Keikoku Railway
 Nikkō is the home city to the Nikkō Ice Bucks in the Asia League Ice Hockey. Nikkō Kirifuri Ice Arena hosted the Women's Ice Hockey World Championships (Division I) in April 2007.
 There is also a speed skating oval.