Beyoğlu is a district located on the European side of Istanbul, Turkey, separated from the old city (historic peninsula of Constantinople) by the Golden Horn. It was known as Pera in the Middle Age and this name remained in common use until the early 20th century and the establishment of the Turkish Republic.

The district encompasses other neighborhoods located north of the Golden Horn, including Galata (the medieval Genoese citadel from which Beyoğlu itself originated), Karaköy, Cihangir, Şişhane, Tepebaşı, Tarlabaşı, Dolapdere and Kasımpaşa, and is connected to the old city center across the Golden Horn through the Galata Bridge and Unkapanı Bridge. Beyoğlu is the most active art, entertainment and night life centre of Istanbul.

The area that is now known as Beyoğlu has been inhabited for millennia, and records show that a settlement existed on the northern shore of the Golden Horn since the time of Christ. In the Greek period, the hillside was covered with orchards and was named Sykai (The Fig Orchard), or Peran en Sykais (The Fig Field on the Other Side), referring to the "other side" of the Golden Horn. As the Byzantine Empire grew, so did Constantinople and its environs. This side of the Golden Horn was built up as a suburb of Byzantium as early as the 5th century. It was in this period that the area began to be called Galata, and a fortress was built by Emperor Theodosius II. The name Galata (possibly derived from the Greek word Galaktos, meaning milk) was presumably given because the area was an important farmland for the city. The Italians, on the other hand, believe the name comes from Calata, meaning downward slope, as Galata, which used to be a Genoese colony, is located on a hilltop that goes downwards to the sea.

The area came to be the base of European merchants, particularly from Genoa and Venice, in what was then known as Pera. Following the Fourth Crusade in 1204, and during the Latin Empire of Constantinople (1204-1261), the Venetians were more prominent in Pera. The Dominican Church of St. Paul (1233), today known as the Arap Camii, is from this period. In 1273, Pera was given to the Republic of Genoa by the Byzantine Emperor Michael VIII Palaeologus in return for Genoa's support of the Empire after the Fourth Crusade and the sacking of Constantinople in 1204. Pera became a flourishing trade colony, ruled by a Podestà. The Genoese Palace (Palazzo del Comune) was built in 1314 by Montano de Marinis, the Podestà of Galata (Pera), and still remains today in ruins, near the Bankalar Caddesi (Banks Street) in Karaköy, along with its adjacent buildings and numerous Genoese houses from the early 1300s. In 1348 the Genoese built the famous Galata Tower, one of the most prominent landmarks of Istanbul. Pera (Galata) remained under Genoese control until May 29, 1453, when it was conquered by the Ottomans along with the rest of the city, after the Siege of Constantinople.

During the Byzantine period, the Genoese Podestà ruled over the Italian community of Galata (Pera), which was mostly made up of the Genoese, Venetians, Tuscans and Ragusans. Following the Turkish siege of Constantinople in 1453, during which the Genoese sided with the Byzantines and defended the city together with them, the Ottoman Sultan Mehmed II allowed the Genoese (who had fled to their colonies in the Aegean Sea such as Lesbos and Chios) to return back to the city, but Galata was no longer run by a Genoese Podestà. Venice, Genoa's archrival, did not miss the opportunity to regain control in the strategic citadel of Galata (Pera), which they were forced to leave in 1261 when the Byzantines retook Constantinople and brought an end to the Latin Empire (1204-1261) that was established by Enrico Dandolo, the Doge of Venice. The Republic of Venice immediately established political and commercial ties with the Ottoman Empire, and a Venetian Baylo (Bailiff) was sent to Pera as a political and commercial ambassador, similar to the role of the Genoese Podestà during the Byzantine period. The Venetians sent Gentile Bellini to Constantinople, who crafted the famous portrait of Sultan Mehmed II, which is found today in the National Portrait Gallery of London. It was also the Venetians who suggested Leonardo da Vinci to Bayezid II when the Sultan mentioned his intention to construct a bridge over the Golden Horn, and Leonardo designed his Galata Bridge in 1502, the sketches and drawings of which are located today in the Museo Nazionale della Scienza e della Tecnologia of Milan. The Baylo's seat was the Venetian Palace, currently the Italian Consulate (and formerly the Italian Embassy until 1923, when Ankara became the new Turkish capital). The Turkish name of Pera, Beyoğlu, comes from the Turkicized form of Baylo, whose palace was the most grandiose structure in this quarter. The name originates from Bey Oğlu (literally Son of Governor) and was particularly used by the Turks to describe Luigi Giritti, son of Andrea Giritti, the Venetian Baylo during the reign of Suleiman the Magnificent. Luigi Giritti's mansion was located close to the present-day Taksim Square. The Ottoman Empire had an interesting relationship with the Republic of Venice. Even though the two states often went to war over the control of East Mediterranean territories and islands, they were keen on restoring their trade pacts once the wars were over, such as the renewed trade pacts of 1479, 1503, 1522, 1540 and 1575 following major sea wars between the two sides. The Venetians were also the first Europeans to taste Ottoman delicacies such as coffee, centuries before other Europeans saw coffee beans for the first time in their lives during the Battle of Vienna in 1683. These encounters can be described as the beginning of today's rich "coffee culture" in both Venice (and later the rest of Italy) and Vienna.

Following the conquest of Constantinople and Pera in 1453, the coast and the low-lying areas were quickly settled by the Turks, but the European presence in the area did not end. During the 19th century it was again home to many European traders, and housed many embassies, especially along the Grande Rue de Péra (today İstiklâl Avenue). The presence of such a prominent European population - commonly referred to as Levantines - made it the most Westernized part of Istanbul, especially when compared to the Old City at the other side of the Golden Horn, and allowed for influxes of modern technology, fashion, and arts. Thus, Beyoğlu was one of the first parts of Istanbul to have telephone lines, electricity, trams, municipal government and even an underground railway, the Tünel, inaugurated in 1875 as the world's second subway line (after London's Underground) to carry the people of Pera up and down from the port of Galata and the nearby business and banking district of Karaköy, where the Bankalar Caddesi (Banks Street), the financial center of the Ottoman Empire, is located. The theatre, cinema, patisserie and café culture that still remains strong in Beyoğlu dates from this late Ottoman period. Shops like İnci, famous for its chocolate mousse and profiteroles, predate the founding of the republic and still survive today.

The foreign communities also built their own schools, many of which went on to educate the elite of future generations of Turks, and still survive today as some of the best schools in Istanbul.

The rapid modernization which took place in Europe and left Ottoman Turkey behind was symbolized by the differences between Beyoğlu, and the historic Turkish quarters such as Eminönü and Fatih across the Golden Horn, in the Old City. When the Ottoman sultans finally initiated a modernization program with the Edict of Tanzimat (Reorganization) in 1839, they started constructing numerous buildings in Beyoğlu that mixed traditional Ottoman styles with newer European ones. In addition, Sultan Abdülmecid stopped living in the Topkapı Palace and built a new palace near Beyoğlu, called the Dolmabahçe Palace, which blended the Neo-Classical, Baroque and Rococo styles.

Adahan building used to be in the 19th century the town mansion of Camondo, a famous Jewish family with a tragic destiny. Comte Moïse de Camondo was born in Istanbul in 1860 into a Sepharadic Jewish family that owned one of the largest banks in the Ottoman Empire and established in France since 1869. When World War I broke out, Nissim, the son of Moise was killed in an air battle in 1917. After this tragic loss, he decided to bedqueath his property in France to the “Arts Décoratifs”, in memory of his son. A museum opened in the the year after Moïse de Camondo died, in 1935. During World War II, his daughter, Béatrice, his son-of-law Léon Reinach and their children, Fanny and Bertrand, died in the nazi camps. The Camondo family died out.