De Roude Léiw (The red lion) is the common name used for the civil ensign of Luxembourg. It can also refer more specifically to the heraldic animal of Luxembourg, which is often used as an emblem or mascot for various institutions and symbols related to Luxembourg.

The ensign consists of a red lion with a golden crown, claws and tongue on a background of ten horizontal bars of blue and white.

Being used since medieval times, the Roude Léiw is seen as one of the most ancient and traditional symbols representing the identity and heritage of the Luxembourgish people.

The ensign is derived from the coat of arms of Luxembourg, which traces its origins back to the 13th century as coat of arms of the House of Luxembourg.

The first sovereign of the House of Luxembourg known to have used a red lion on a blue and white striped background was Henry V the Blond (1216-1281), Count of Luxembourg. Since then, the design has remained mostly unchanged.

It has been used as standard and coat of arms of the counts, and later the dukes of Luxembourg.

In 1972, the Roude Léiw was for the first time declared to be an official symbol of the Grand-Duchy of Luxembourg by law. Since then, the Roude Léiw was used as the official naval and civil ensign of Luxembourg.

Article 4 of the Law of the 23th of June 1972 concerning the national emblems sets the appearance of the Roude Léiw as the civil ensign as follows: