Baguio (UK: /ˈbæɡioʊ/ BAG-ee-oh, US: /ˈbɑːɡioʊ, ˌbɑːɡiˈoʊ/ BAH-ghee-oh, -⁠OH, Tagalog: [ˈbaɡjo]), officially the City of Baguio (Ibaloi: Siudad ne Bagiw; Ilocano: Siudad ti Baguio; Tagalog: Lungsod ng Baguio), is a highly urbanized city in the Cordillera Administrative Region, Philippines. It is known as the "Summer Capital of the Philippines", owing to the city's cool climate relative to the lowlands. With an approximate elevation of 1,500 meters (4,900 feet) above mean sea level, Baguio belongs to the Luzon tropical pine forests ecoregion; the climate is conducive for the growth of mossy plants, orchids and pine trees, to which it attributes its other moniker as the "City of Pines".

Baguio was established as a hill station by the United States in 1900 at the site of an Ibaloi village known as Kafagway. It was the United States' only hill station in Asia.

Baguio is classified as a highly urbanized city (HUC). It is the largest city in Benguet, serving as the provincial capital from 1901 to 1916, but has since been administered independently from the province following its conversion into a chartered city. Baguio is geographically located within the province of Benguet by the Philippine Statistics Authority for its geographical and statistical purposes only. The city is the center of business, commerce, and education in northern Luzon, as well as the most populous and seat of government of the Cordillera Administrative Region.

As of 2025 the City of Baguio has an estimated population of approximately 407,000 residents. This figure reflects a steady annual growth rate of around 1.75% from the previous year. The population has been gradually increasing over the past decade, with notable growth from 366,358 in 2020 to 392,000 in 2023. The city is also part of the larger Baguio Metropolitan Area, which includes surrounding municipalities and has a combined population of about 451,844 as of 2024.

Baguio was called Kafagway by indigenous peoples. The name Baguio originated in the American period and is derived from the Ibaloi word bagiw (moss), which was then Hispanicized as Baguio. A demonym for natives of the city, Ibagiw, is also derived from it. It is also the name for the city's annual arts festival.

Baguio used to be a vast mountain zone with lush highland forests, teeming with various wildlife such as the indigenous deer, cloud rats, Philippine eagles, Philippine warty pigs, and numerous species of flora. The area was a hunting ground of the indigenous peoples, notably the Ibalois and other Igorot ethnic groups. When the Spanish arrived in the Philippines, the area was never fully subjugated by Spain due to the intensive defense tactics of the indigenous Igorots of the Cordilleras.

Igorot oral history states the Benguet upper class, baknang, was founded between 1565 and the early 1600s, by the marriage of a gold trader, Amkidit, and a Kankanaey maiden gold panning in Acupan. Their son, Baruy, discovered a gold deposit in the area, which he developed with hired workers and slaves.

In 1755, the Augustinian Fray Pedro de Vivar established a mission in Tonglo (Tongdo) outside Baguio. Before he was driven out the following year, this rancheria included 220 people, including several baknang families. The Spanish tried to regain the mission in 1759, but were ambushed. This prompted Governor General Pedro Manuel de Arandía Santisteban to send Don Manuel Arza de Urrutia on a punitive expedition, which resulted in the mission being burned to the ground.