The Order Pour le Mérite, known informally as the Blue Max (German: Blauer Max), was Prussia's highest military order until the end of World War I.

The award was first founded in 1740 by Friedrich the Great, named in French, the language of the royal court, for merit. Until 1810 the award was both a civilian and military honor. In January of that year, Prussian King Friedrich Wilhelm III decreed that the award could only be presented to serving military personnel.

In 1842, King Friedrich Wilhelm IV founded the civil class of the award, the Pour le Mérite for Science and Arts (Pour le Mérite für Wissenschaften und Künste), with the three sections: humanities, natural science and fine arts. One of the most famous artists who received the civil class of Pour le Mérite was Käthe Kollwitz. She was deprived of it later by the Nazi government.

The medal was a blue enameled Maltese Cross with eagles between the arms, and the royal cipher and the words Pour le Mérite on the cross.

In 1866 a special military Grand Cross class of the award was established. This grade of the award was given to those who, through their actions, caused the retreat or destruction of an army. Although many in the military hierarchy wished to award Manfred von Richthofen this grade of the Pour le Mérite, he was ineligible because of this stipulation. Therefore, Prussia resorted to the expedient of giving Richthofen a slightly less prestigious honor, the rarely-awarded Order of the Red Eagle.

The award gained international fame during World War I. Although it could be awarded to any military officer, its most famous recipients were the pilots of the German air arm, whose exploits were celebrated in wartime propaganda. In the aerial war a fighter pilot was initially entitled to the award upon downing eight enemy aircraft. Ace Max Immelmann was the first airman to receive the award, after which it became known among his fellow pilots, on account of its color and its recipient, as the Blue Max.

The number of aircraft downed to receive the award continued to increase during the war; by early 1917 it required destroying sixteen (16) enemy airplanes, and by war's end the approximate figure was thirty (30). However, other aviation recipients included Zeppelin commanders, bomber and observation crews, and at least one balloon observer.

Recipients of the Blue Max were required to wear the badge whenever in uniform.

Notable recipients included Field Marshal Leonhard Graf von Blumenthal, Manfred von Richthofen, better known as the "Red Baron", Hermann Göring, who later became one of the most senior leaders of the Third Reich, Erwin Rommel, the famed "Desert Fox" of WWII, Kress von Kressenstein, and Paul von Lettow-Vorbeck , who led German forces in the guerrilla campaign in German East Africa. The last living holder of the Pour le Mérite was novelist Ernst Jünger, who died in 1998.

Although many of its most famous recipients were junior officers, especially pilots, more than a third of all awards went to generals and admirals. Junior officers (army captains and lieutenants and their navy equivalents) accounted for only about 25% of all awards. Senior officer awards tended to be more for outstanding leadership in combat than for individual acts of bravery.

The award was abolished with Kaiser Wilhelm II's abdication on 9 November 1918.

In 1952, the President of West Germany, Theodor Heuss, revived the civil class of the order as an autonomous organization under the protection of the German President (although it is not a state order like the Bundesverdienstkreuz). This revived civil order is awarded for achievements in the arts and sciences, rather than for military merit. Laureates of the present are e.g. Wim Wenders (filmmaker), Rudolf Mößbauer (physicist and Nobel Prize winner) and Umberto Eco (writer).