The Bosphorus Bridge (Turkish: Boğaziçi Köprüsü), known officially as the 15 July Martyrs Bridge (Turkish: 15 Temmuz Şehitler Köprüsü) and colloquially as the First Bridge (Turkish: Birinci Köprü), is the oldest and southernmost of the three suspension bridges spanning the Bosphorus strait (Turkish: Boğaziçi) in Istanbul, Turkey, thus connecting Europe and Asia (alongside the Fatih Sultan Mehmet Bridge and Yavuz Sultan Selim Bridge). The bridge extends between Ortaköy (in Europe) and Beylerbeyi (in Asia).

It is a gravity-anchored suspension bridge with steel towers and inclined hangers. The aerodynamic deck hangs on steel cables. It is 1,560 m (5,118 ft) long with a deck width of 33.40 m (110 ft). The distance between the towers (main span) is 1,074 m (3,524 ft) and the total height of the towers is 165 m (541 ft). The clearance of the bridge from sea level is 64 m (210 ft).

Upon its completion in 1973, the Bosphorus Bridge had the fourth-longest suspension bridge span in the world, and the longest outside the United States (only the Verrazzano–Narrows Bridge, Golden Gate Bridge and Mackinac Bridge had a longer span in 1973). The Bosphorus Bridge remained the longest suspension bridge in Europe until the completion of the Humber Bridge in 1981, and the longest suspension bridge in Asia until the completion of the Fatih Sultan Mehmet Bridge (Second Bosphorus Bridge) in 1988 (which was surpassed by the Minami Bisan-Seto Bridge in 1989). Currently, the Bosphorus Bridge has the 45th-longest suspension bridge span in the world.

After a group of soldiers took control and partially closed off the bridge during the military coup d'état attempt on 15 July 2016, Prime Minister Binali Yıldırım proclaimed on 25 July 2016 the decision of the Cabinet of Turkey that the bridge will be formally renamed as the 15 Temmuz Şehitler Köprüsü (July 15th Martyrs Bridge) in memory of those killed while resisting the attempted coup.

The Bosphorus Bridge is famous for its important transport routes, connecting parts of Europe to Turkey.

The idea of a bridge crossing the Bosphorus dates back to antiquity. The Greek writer Herodotus says in his Histories that, on the orders of Emperor Darius the Great of the Achaemenid Empire (522 BC–485 BC), Mandrocles of Samos once engineered a pontoon bridge across the Bosphorus, linking Asia to Europe; this bridge enabled Darius to pursue the fleeing Scythians as well as position his army in the Balkans to overwhelm Macedon. The first modern project for a permanent bridge across the Bosphorus was proposed to Sultan Abdul Hamid II of the Ottoman Empire by the Bosphorus Railroad Company in 1900, which included a rail link between the continents.

The decision to build a bridge across the Bosphorus was taken in 1957 by Prime Minister Adnan Menderes. For the structural engineering work, a contract was signed with the British firm Freeman Fox & Partners in 1968. The bridge was designed by the British civil engineers Gilbert Roberts, William Brown and Michael Parsons, who also designed the Humber Bridge, Severn Bridge, and Forth Road Bridge. David B Steinman, an American engineer who had recently designed the Mackinac Bridge was also contracted, but died early on in the design process in 1960. Construction started in February 1970 and ceremonies were attended by President Cevdet Sunay and Prime Minister Süleyman Demirel. The bridge was built by the Turkish firm Enka Construction & Industry Co. along with the co-contractors Cleveland Bridge & Engineering Company (England) and Hochtief AG (Germany).

The bridge was completed on 30 October 1973, one day after the 50th anniversary of the founding of the Republic of Turkey, and opened by President Fahri Korutürk and Prime Minister Naim Talu. The cost of the bridge was US$200 million ($1.45 billion in 2025 dollars).