The national flag of Denmark (Danish: Dannebrog, pronounced [ˈtænəˌpʁoˀ]) is red with a white Nordic cross, which means that the cross extends to the edges of the flag and the vertical part of the cross is shifted to the hoist side.

A banner with a white-on-red cross is attested as having been used by the kings of Denmark since the 14th century. An origin legend with considerable impact on Danish national historiography connects the introduction of the flag to the Battle of Lindanise of 1219. The elongated Nordic cross reflects the use as a maritime flag in the 18th century. The flag became popular as a national flag in the early 16th century. Its private use was outlawed in 1834, but again permitted by a regulation of 1854. The flag holds the world record of being the oldest continuously used national flag.