The 250th Infantry Division (German: 250. Infanterie-Division), better known as the Blue Division (Spanish: División Azul, German: Blaue Division), was a unit of volunteers from Francoist Spain operating from 1941 to 1943 within the German Army (Heer) on the Eastern Front during World War II. It was officially designated the Spanish Volunteer Division (División Española de Voluntarios) by the Spanish Army.

Francisco Franco had secured power in Spain after the Nationalist victory in the Spanish Civil War (1936–1939), during which the Nationalists received support from Nazi Germany. Franco's authoritarian regime remained officially non-belligerent in World War II but sympathised with the Axis powers. After lobbying by the Spanish Foreign Minister Ramón Serrano Suñer and by senior figures within the Spanish Army following the 22 June 1941 launch of Operation Barbarossa, Franco agreed that Spanish people would be permitted to enlist privately in the German Army and undertook to provide tacit support. An infantry division was raised from Falangist and Spanish Army cadres and was sent for training in Germany. The unit fought on the Eastern Front, in the 1941–1944 siege of Leningrad, notably in the Battle of Krasny Bor. They eventually withdrew from the front after Allied political pressure on Spain in October 1943 and returned to Spain shortly afterwards. Several thousand non-returners were incorporated into the 121st Infantry Division, the short-lived Blue Legion, and eventually into the Waffen-SS.

Francisco Franco took power at the head of a coalition of fascist, monarchist, and conservative political factions in the Spanish Civil War (1936–1939) against the left-leaning Spanish government supported by communist and anarchist factions. More than 300,000 people were killed, and lasting damage was done to the country's economy.

While Spain formally remained neutral, it did not hide its ideological support for the Axis powers. Franco had been supported by Nazi Germany and Fascist Italy during the Civil War and Franco sympathised with many aspects of fascist ideology, especially its anti-communism. On the other side, the Republican army had been supported by Soviet aid. More importantly, Franco seriously contemplated joining the Axis Powers in the aftermath of the Fall of France in 1940. He met Adolf Hitler on 23–24 October 1940 at Hendaye to discuss Spanish belligerency but was unable to gain promises that Spain would gain colonial territories from France in North Africa. Hitler feared delegitimizing the new Vichy regime in France.

The German invasion of the Soviet Union led to renewed interest in participating in what Spanish officials saw as an "anti-communist crusade". Within hours of the invasion on 22 June 1941, Foreign Minister Ramón Serrano Suñer first proposed to Franco the idea of a Spanish contribution, publicly declaring the Soviet Union guilty of the Spanish Civil War. Senior officers of the Spanish Army supported the proposal. Franco soon agreed to the proposal, directing that the Spanish Army should unofficially co-ordinate the formation of the unit. Although disappointed that Spain had not declared war on the Soviet Union, the German regime accepted the Spanish offer on 24 June 1941. Franco struggled to balance the demands of the Spanish Army and Falangist factions, both of which attempted to influence the new unit, himself siding with the former.

Recruitment began on 27 June 1941 and 18,373 men had volunteered by 2 July 1941 from within the Spanish Army and Falangist movement. Fifty per cent of officers and NCOs were professional soldiers given leave from the Spanish Army, including many veterans of the Spanish Civil War.^{[citation needed]} The division was made up mainly of Falangist volunteers and almost a fifth of early volunteers were students. Additionally, the division contained a small number of White émigrés from Spain. General Agustín Muñoz Grandes was assigned to lead the volunteers. Because the soldiers could not use official Spanish Army uniforms, they adopted a symbolic uniform comprising the red berets of the Carlists, the khaki trousers of the Spanish Legion, and the blue shirts of the Falangists—hence the nickname "Blue Division." This uniform was used only while on leave in Spain; in the field, soldiers wore the German Army field grey uniform (Feldgrau) with a shield on the upper right sleeve bearing the word "España" (Spanish for "Spain") and the Nationalist Spanish national colours.

On 13 July 1941 the first train left Madrid for Grafenwöhr, Bavaria for a further five weeks of training. There they became the German Army's 250th Infantry Division and were initially divided into four infantry regiments, as in a standard Spanish division. To aid their integration into the German supply system, they soon adopted the standard German model of three regiments. One of the original regiments was dispersed amongst the others, which were then named after three of the Spanish cities that volunteers largely originated from—Madrid, Valencia and Seville. Each regiment had three battalions (of four companies each) and two weapons companies, supported by an artillery regiment of four battalions (of three batteries each). There were enough men left over to create an assault battalion, mainly armed with submachine guns. Later, due to casualties, this unit was disbanded. Aviator volunteers formed a Blue Squadron (Escuadrillas Azules) which, using Messerschmitt Bf 109s and Focke-Wulf Fw 190s, claimed to have shot down 156 Soviet aircraft.

On 31 July, after taking the Hitler Oath, the Blue Division was formally incorporated into the German Wehrmacht as the 250th Division. It was initially assigned to Army Group Center, the force advancing towards Moscow. The division was transported by train to Suwałki, Poland (August 28), from where it had to continue by foot on a 900-kilometre (560 mi) march. It was scheduled to travel through Grodno, and Lida in Belarus, Vilnius (Lithuania), and Maladzyechna, Minsk, and Orsha in Belarus to Smolensk, and from there to the Moscow front. While marching towards the Smolensk front on September 26, the Spanish volunteers were rerouted from Vitebsk and reassigned to Army Group North (the force closing on Leningrad), becoming part of the German 16th Army. The Blue Division was first deployed on the Volkhov River front, with its headquarters in Grigorovo, on the outskirts of Novgorod. It was in charge of a 50-kilometre (31 mi) section of the front north and south of Novgorod, along the banks of the Volkhov River and Lake Ilmen.