Braunschweig (German: [ˈbʁaʊnʃvaɪk] ^ⓘ) or Brunswick (English: /ˈbrʌnzwɪk/ BRUN-zwik; from Low German Brunswiek, local dialect: Bronswiek [ˈbrɔˑnsviːk]) is a city in Lower Saxony, Germany, north of the Harz Mountains at the farthest navigable point of the river Oker, which connects it to the North Sea via the rivers Aller and Weser. In 2024, it had a population of 272,417. The Braunschweig-Wolfsburg-Salzgitter region had 1.02 million residents including the cities Wolfsburg and Salzgitter, it is the second largest urban center in Lower Saxony after Hanover. The urban agglomeration of Braunschweig had a population of 551,000 with almost 45% having a migration background, making it the most diverse urban agglomeration in the whole state. The city consists of 37.5% immigrants (approximately 102,000) with a high number of migrants coming from other European countries, Asia and Africa. 73% of the Germans residing in Braunschweig come from different parts of the country, particularly North Rhine Westphalia, Hessen and the former states of East Germany. Braunschweig is considered an important regiopolis. It is one of the largest regiopolitan cities in Northern Germany and the largest regiopolis in Lower Saxony. The city is seen as a major hub within the region due to it having multiple characteristics of a metropolitan city in a smaller scale or in a comparative amount to other metropolitan cities in Germany.

127.12 km² (49 sq. mi.) of the city's area is made up of greenspaces such as parks and forests. Braunschweig has a population density of 4,121 per km² (10,673 per sq. mi.) excluding the green areas because only about 66 km² (25½ sq. mi.) of the total area is properly urban, making it quite a dense city. Many districts of the city have a density over 4,450 people per square kilometer (11,525 per sq. mi.) such as Weststadt, Innenstadt, Westliches Ringgebiet, Nordstadt, or Östliches Ringgebiet. Due to the city's limited urban core and efforts in preserving green spaces, 81% of the residential buildings are multi-storey apartments limiting 74% of the flats with a space below 100 square meters (1000 sq. ft.). The city is constructing more residential areas within city limits so that by 2030 the population increases by 15.000 from 2014.

A powerful and influential centre of commerce in medieval Germany, Brunswick was a member of the Hanseatic League from the 13th until the 17th century. It was the capital city of three successive states: the Principality of Brunswick-Wolfenbüttel (1269–1432, 1754–1807, and 1813–1814), the Duchy of Brunswick (1814–1918), and the Free State of Brunswick (1918–1946).

Today, Brunswick is the second-largest city in Lower Saxony and a major centre of scientific research and development.

The date and circumstances of the town's foundation are unknown. Tradition maintains that Brunswick was created through the merger of two settlements, one founded by Brun(o), a Saxon count who died in 880, on one side of the River Oker – the legend gives the year 861 for the foundation – and the other the settlement of a legendary Count Dankward, after whom Dankwarderode Castle (the "Castle of Dankward's clearing"), which was reconstructed in the 19th century, is named.

The town's original name of Brunswik may be a combination of the name Bruno and Low German wik (related to the Latin vicus), a place where merchants rested and stored their goods. The town's name, therefore, may indicate a resting place, consistent with its location by a ford across the Oker River. An alternative explanation of the city's name is that it comes from Brand, or burning, indicating a place which developed after the landscape was cleared through burning. The city was first mentioned in documents from the St. Magni Church from 1031, which give the city's name as Brunesguik.

Up to the 12th century, Brunswick was ruled by the Saxon noble family of the Brunonids; then, through marriage, the town fell to the House of Welf. In 1142, Henry the Lion of the House of Welf became duke of Saxony and made Braunschweig the capital of his state (which, from 1156 on, also included the Duchy of Bavaria). He turned Dankwarderode Castle, the residence of the counts of Brunswick, into his own Pfalz and developed the city further to represent his authority. Under Henry's rule, the Cathedral of St. Blasius was built and he also had the statue of a lion, his heraldic animal, erected in front of the castle. The lion subsequently became the city's landmark.^{[citation needed]}

Henry the Lion became so powerful that he dared to refuse military aid to the Emperor Frederick I Barbarossa, which led to his banishment in 1182. Henry went into exile in England. He had previously established ties to the English crown in 1168, through his marriage to King Henry II of England's daughter Matilda, sister of Richard the Lionheart. However, Henry's son Otto, who regained influence and was eventually crowned Holy Roman Emperor, continued to foster the city's development.^{[citation needed]}