Northbrook is a village in Cook County, Illinois, United States. It is a suburb of Chicago in the greater North Shore, part of a collection of upscale residential communities north of Chicago. The population was 35,222 at the 2020 census. It is within Northfield Township, Illinois, bordering Lake County.

When incorporated in 1901, the village was known as Shermerville in honor of Frederick Schermer, who donated the land for its first train station. The village changed its name to Northbrook in 1923 as an effort to improve its public image. The name was chosen because the West Fork of the North Branch of the Chicago River runs through the village.

Glenbrook North High School, founded in 1953 as Glenbrook High School, is located in Northbrook. The village is also home to the Northbrook Park District, the Northbrook Court shopping mall, the Ed Rudolph Velodrome, the Chicago Curling Club, and the Northbrook Public Library.

Members of the Potawatomi tribe were the earliest recorded residents of the Northbrook area. After signing the 1833 Treaty of Chicago, the Potawatomi ceded their Illinois lands and moved to a place near Council Bluffs, Iowa. Afterward, Joel Sterling Sherman moved from Connecticut with his family and bought 159 acres (64 ha) of land in the northwest quarter of Section 10 for $1.25 per acre; Northbrook's downtown is located on this site. A German immigrant named Frederick Schermer donated a portion of the land he bought from Sherman to be used for the town's first railroad station, which was named after him. By the 1870s, Shermerville (which also took its name from Shermer) was a farming community. In 1901 the community was incorporated as the Village of Shermerville after a close referendum for incorporation. At the time of incorporation, it had 311 residents and 60 houses. In these early years, Shermerville became notorious for rowdy gatherings at its five saloons; by 1921, therefore, residents believed that the name "Shermerville" had a negative reputation and sought to change it. A renaming contest was held, and the name "Northbrook" was submitted by the US postmaster (and then President of the National Rural Letter Carriers' Association) Edward Landwehr. Landwehr was the son of Herman and Anna Helene Landwehr, both German immigrants and early settlers in the community and for whose family Landwehr Road in Northbrook is named. In 1923, "Northbrook", the winning name, was adopted. At the time, Northbrook had 500 residents. Later on, after the end of World War II, Northbrook's population began to rapidly increase. In 1997, President Bill Clinton visited Northbrook to congratulate the 8th-grade students of Northfield Township (which is mainly Northbrook) for getting the highest score on a world science test, and for getting the second-highest score on a world math test. Between 1950 and 1980, the town's population rose from 3,319 to 30,735. Northbrook was the first community not bordering Lake Michigan to filter Lake Michigan water for public use. Owing to the suburbanization of the community, the last working farm in Northbrook, the Wayside Farm, was sold and closed in 1987.

Northbrook is a suburb of the city of Chicago, located at 42°7′45″N 87°50′27″W / 42.12917°N 87.84083°W / 42.12917; -87.84083 (42.129226, −87.840715). in the extreme northeastern region of Illinois. Whilst the vast majority of the village lies within Northfield Township, its northwest corner is situated in Wheeling Township. Northbrook shares a border with Northfield to its southeast, Glenview and Prospect Heights to its southwest and south, Glencoe directly east, Highland Park to its northeast, Deerfield directly north, Riverwoods to its northwest, and Wheeling directly west. Techny, once a separate community, was annexed by Northbrook in 1989 and predominantly lies south of Voltz Road and stretches south to border Glenview. Interstate 294 curves along Northbrook's western edge while the Edens Spur marks most of the village's northern boundary. Illinois Route 68 stretches west from Wheeling into Northbrook, terminating at the Edens Expressway near Glencoe. In addition, a portion of Illinois Route 43 cuts through Northbrook.

According to the 2020 US gazetteer files, the village has a total area of 13.30 square miles (34.4 km²; 3,440 ha), of which 13.24 square miles (34.3 km²; 3,430 ha) (or 99.55%) is land, and 0.07 square miles (0.18 km²; 18 ha) (or 0.45%) is water. Situated along the West Fork of the North Branch of the Chicago River, Techny Prairie Park and Fields is the largest park in Northbrook at 113.82 acres and features picnic areas, a sled hill, batting cages, the nine-hole Anetsberger Golf Course and Techny Prairie Activity Center, a 44,200 square foot facility housing fitness equipment and studios, an indoor track, pickleball courts, and more. One of the biggest lakes in Northbrook, Lake Shermerville, is located within Wood Oaks Green Park, a 55.9 acre open space with fishing platforms, tennis courts, a playground, bike trail, and more. Northbrook lies within the Chicago/Calumet Rivers watershed.

From 1947 until 1988, Northbrook used a single area code, 312. However, in 1988, the 312 area code was made exclusive to Chicago and the 708 area code was introduced. Then, in 1996, the 708 area code was split into three: 708, 630, and 847. Currently, Northbrook uses the 847 area code as well as the 224 area code which was introduced in 2002.

Due to its proximity to the city, Northbrook's climate shares many of the same traits as Chicago. Northbrook lies in a humid continental climate zone (Köppen: Dfa) and experiences four distinct seasons. Northbrook receives an average of 37.82 inches (961 mm) of precipitation each year. According to MyForecast, Northbrook's record high is 104 °F (40 °C), and the record low is -24 °F (-31.1 °C). Summers are hot and humid, with frequent heat waves. July is the hottest month, and the daily average temperature is 82 °F (27.7 °C), while the daily low temperatures are around 66 °F (18.8 °C). On average, summer temperatures reach at least 90 °F (32 °C) on as many as 16 days. Winters are relatively cold and snowy, with blizzards sometimes occurring, as in 2011. There are many sunny but cold days in winter. The average winter high from December through March is about 36 °F (2.2 °C), with January and February being the coldest months; a polar vortex occurred in January 2019. Spring and autumn are mild, short seasons. Dew point temperatures in the summer range from an average of 56 °F (13.3 °C) in June to 62 °F (16.7 °C) in July. Like all Chicago suburbs, Northbrook lies within USDA plant hardiness zone 5b.