The Valtellina Redoubt or, officially, in Italian: Ridotto Alpino Repubblicano (transl.  Republican Alpine Redoubt) or RAR, was the intended final stronghold or redoubt of the Italian fascist regime of Benito Mussolini at the end of World War II in Europe. It was to be based in the Valtellina, a valley in the Italian Alps, which had the natural protection afforded by the surrounding mountains as well as the possibility of re-using fortifications built in the area for World War I. The idea was initially proposed in September 1944 by Alessandro Pavolini, one of the fascist leaders, who saw it as the place for the regime to make a "heroic" last stand which would inspire a future fascist revolution.

Although Pavolini's idea was supported by Mussolini, the fascist leadership as a whole was divided over it. Only minimal preparatory work was carried out to establish the area as a stronghold and, as a result, when the Allied victory in Italy approached in April 1945, the Valtellina was not ready to be used by the fascists as a redoubt. At the end of April, resistance to the Allied advance quickly collapsed without any major "last stand", and the war in Italy soon ended with the Axis forces signing the Surrender of Caserta on 29 April 1945.

With the fall of the Fascist regime in Italy in July 1943 following the Allied invasion of Sicily, Mussolini was deposed as dictator and placed under arrest. In September of that year, the Allies launched the invasion of mainland Italy from the south. In the same month, German special forces rescued Mussolini in the Gran Sasso raid and Hitler installed him as leader of the Italian Social Republic, a German puppet state in the Axis-controlled northern half of the country, and based at the town of Salò near Lake Garda. By 1944, the "Salò Republic", as it came to be called, was threatened not only by the Allies advancing from the south but also internally by Italian anti-fascist partisans, in a brutal conflict that was to become known as the Italian civil war.

Slowly fighting their way up the Italian peninsula, the Allies took Rome and then Florence in the summer of 1944 and later that year they began advancing into northern Italy. With the final collapse of the German army's Gothic Line in April 1945, total defeat for the Salò Republic and its German protectors was imminent.

In September 1944, Alessandro Pavolini proposed that the regime create an "Alpine stronghold", the Ridotto Alpino Repubblicano ("Republican Alpine Redoubt" or RAR), to mount a last stand against the Allied advance. Pavolini was Fascist Party secretary and founder of the Black Brigades, the regime's paramilitary force and successor to the by then disbanded Blackshirts. The objective of making a last stand in an Alpine stronghold, according to Pavolini, would be to set a heroic example for later generations to follow and, after the inevitable defeat, to inspire a future fascist revolution. The concept was that the stronghold would be well supplied with food and weaponry, defended by elite troops and not dependent on the Germans. Pavolini wrote to Mussolini on 8 September:

Duce, the project – in the deplorable event of a further and almost complete invasion of republican territory  – to entrench ourselves with the Blackshirts, our weapons and our government in a defensible area such as the province of Sondrio and part of Como would, it seems to me, be the most logical and worthwhile solution... On the other hand, our resistance in the Valtellina and around Adamello would protect the German flank in South Tyrol. From every point of view, it seems to me, the political and ideal advantage of our ally coincides with our own.

Besides the Valtellina, three other areas were considered. Some in the fascist leadership favoured Val d'Aosta or even Trieste, the latter because its location had echoes of the 1919 Impresa di Fiume. Others preferred South Tyrol. As most of the Italian Alps was under German control and the partisans had taken the areas west of South Tyrol, the only area that potentially could be utilised was the Valtellina, an Alpine valley entered from the northern end of Lake Como.

As a possible stronghold the Valtellina had a number of advantages. The 71 kilometre (44 mi) long valley was protected by mountains and easily defended, had hydroelectric power stations and a hospital even though it was sparsely populated, and was still surrounded by World War I fortifications. Some of these were part of the Cadorna Line defensive system. The western entrance to the valley was covered by the fort of Montecchio, built between 1911 and 1915, which had four armoured turrets with Schneider 145mm cannons. Other forts protected the eastern entrance to the valley, for example, Forte Venini di Oga, which had been built between 1908 and 1912 to defend the passes of the Upper Valtellina. However, it would require some effort to remove the partisans operating in the area. Pavolini strongly advocated the Valtellina, and objected to the South Tyrol, in particular, because it was under German control. On the other hand, Rudolf Rahn, the German Ambassador, advised Mussolini against the Valtellina as he thought the proximity of Switzerland would encourage desertions amongst the troops.