Cologne Cathedral (German: Kölner Dom, officially Hohe Domkirche Sankt Petrus, English: Cathedral Church of Saint Peter) is a Catholic cathedral in Cologne, North Rhine-Westphalia. It is the seat of the Archbishop of Cologne and of the administration of the Archdiocese of Cologne. It is a renowned monument of German Catholicism and Gothic architecture and was declared a World Heritage Site in 1996. It is Germany's most visited landmark, attracting an average of 20,000 people a day. At 157 m (515 ft), the cathedral is the tallest twin-spired church in the world, the second tallest church in Europe after Ulm Minster, and the third tallest church of any kind in the world. It is the largest Gothic church in Northern Europe and has the second-tallest spires. The towers for its two huge spires give the cathedral the largest façade of any church in the world. The choir has the largest height-to-width ratio, 3.6:1, of any medieval church.

Construction of Cologne Cathedral began in 1248 but was halted in the years around 1560, unfinished. Attempts to complete the construction began around 1814 but the project was not properly funded until the 1840s. The edifice was completed to its original Medieval plan in 1880. Cologne's medieval builders had planned a grand structure to house the reliquary of the Three Kings and fit for its role as a place of worship for the Holy Roman Emperor. Despite having been left incomplete during the medieval period, Cologne Cathedral eventually became unified as "a masterpiece of exceptional intrinsic value" and "a powerful testimony to the strength and persistence of Christian belief in medieval and modern Europe". Only the telecommunications tower is higher than the cathedral.

 The cathedral suffered fourteen hits by aerial bombs during World War II. Badly damaged, it nevertheless remained standing in an otherwise completely flattened city. The twin spires were an easily recognizable navigational landmark for Allied aircraft bombing.On 6 March 1945, an area west of the cathedral (Marzellenstrasse/Trankgasse) was the site of intense combat between American tanks of the 3rd Armored Division and a Panther Ausf. A of Panzer brigade 106 Feldherrnhalle. A nearby Panther, a German medium tank, was sitting by a pile of rubble near a train station right by the twin spires of the Cologne Cathedral. The Panther successfully knocked out two Sherman tanks, killing three men, before it was destroyed by a T26E3 Pershing, nicknamed Eagle 7, minutes later. Footage of that battle survives. The destroyed Panther was later put on display at the base of the cathedral for the remainder of the war in Europe.

Repairs of the war damage were completed in 1956. A repair to part of the northwest tower, carried out in 1944 using poor-quality brick taken from a nearby ruined building, remained visible as a reminder of the war until 2005, when it was decided to restore the section to its original appearance. To investigate whether the bombings had damaged the foundations of the Dom, archaeological excavations began in 1946 under the leadership of Otto Doppelfeld and were concluded in 1997. One of the most meaningful excavations of churches, they revealed previously unknown details of earlier buildings on the site.

Repair and maintenance work is constantly being carried out in one or another section of the building, which is rarely completely free of scaffolding, as wind, rain, and pollution slowly eat away at the stones. The Dombauhütte, established to build the cathedral and keep it in repair, is said to employ the best stonemasons in the Rhineland. Half the costs of repair and maintenance are still borne by the Dombauverein.