Berlinka (Russian: Берлинка) is the informal Polish and Russian name given to sections of the unfinished Reichsautobahn Berlin-Königsberg, which was a pre-World War II German Reichsautobahn project to connect Berlin with Königsberg in East Prussia. In the late 1930s, the sections near these two cities were finished, but not the larger section in between. The German demand in 1939 to run this road across the Polish Corridor with extraterritorial status and Poland's refusal to allow this were used by Nazi Germany as a pretext to start a war. During the war, the Germans did not continue construction on a large scale and the route was never built. After the war, the German Democratic Republic, the Polish People's Republic and the Soviet Union's Kaliningrad Oblast inherited the remnants.

Eastern Prussia had been separated from Germany following the Treaty of Versailles by the Polish Corridor of the Second Polish Republic. By 1939, Poland had already refused demands made by Nazi Germany, including one for an extraterritorial corridor within the Polish territory. This fact was eventually used by Adolf Hitler as one of the pretexts for the German invasion of Poland in 1939.

The road was planned under the Weimar Republic, but was partially constructed during the 1930s and early 1940s by the Third Reich.

Following territorial changes made after World War II it ran through three countries: the Soviet Union's Kaliningrad Oblast (today an exclave of the same name, in post-1991 Russia), Poland, and what had been East Germany through to October 1990. Its original purpose gone, some segments of the road were incorporated into local road networks while most of it fell into disrepair. The border between the Kaliningrad Oblast and Poland was completely sealed to civilian traffic during the Cold War, given the high density of Soviet military installations in that area, which ensured the Berlinka section in that area saw almost no use. The border between Poland and East Germany was open to civilian traffic but the economies of the two countries were not well connected and auto traffic between them was not significant for many decades. Given these conditions, some segments of Berlinka became a minor tourist attraction in the years after the war, as an example of a Nazi-built autobahn preserved in an almost pristine state, carrying very little or no traffic. A number of movies made in Poland and the USSR that were set in Germany had their autobahn scenes shot on Berlinka sections. A popular Polish book and television series about Pan Samochodzik had a high speed car chase that was set on Berlinka (as at the time one of the few places in Poland where a high speed car chase was even plausible, given the execrable condition of other roads). In recent years that attraction has diminished as most of the stretches completed in the 1930s have been reconstructed to modern standards and largely lost their original appearance. Today the last remaining stretch in Poland that still has Nazi era construction features is signed as voivodeship road 142, north-east of Szczecin. As that stretch is only a local road, it is unlikely to be rebuilt in the foreseeable future. On the Russian side, the remains of the old road are still visible (54°31′35″N 20°17′01″E / 54.5264296°N 20.2836840°E / 54.5264296; 20.2836840) next to the E28 highway from the Polish-Russian border to the ring road of the city of Kaliningrad.

Along with constructing the motorway, after invading Poland, the Germans also quickly upgraded the main road going to East Prussia, in places paving it with concrete. Even though it is only a single carriageway road and not a motorway, it is also considered to be a part of the Berlinka's route. This section includes one interesting cloverleaf interchange (54°02′54″N 18°45′40″E / 54.04836°N 18.7610°E / 54.04836; 18.7610) some 34.5 kilometres (21.4 miles) south-southeast of Gdańsk, and a large bridge over the Vistula south of Tczew (54°03′07″N 18°49′00″E / 54.05205°N 18.81676°E / 54.05205; 18.81676).

Construction began in late 1933, using unemployed German workers as part of the state's reforms to counteract the Great Depression, the construction of the Reichsautobahn (RAB) network. The first 113 kilometre (70 mile) long segment near Stettin (now Szczecin), Stettiner Dreieck to Stettin-Süd, was opened on September 27, 1936. The segment from Königsberg to Elbing (now Elbląg) was opened in 1937. In 1937, beltways near Stettin and Elbing were built.

In 1938, work slowed as Germany geared up for war, and workers were directed to other projects. The highway featured prominently in Nazi political rhetoric of 1939, as Hitler's demands included an extraterritorial corridor—the Danzig Corridor through the Polish Corridor—which would connect Germany to Eastern Prussia. This, alongside other demands, was refused by the Polish government, and Hitler used this as one of the pretexts for the invasion of Poland in September 1939.

By October 1939, Poland was defeated, and work on the Berlinka resumed. The labour pool was increasingly composed of conscript workers from Poland. The Bäderstraße (near Rzęśnica and Wielgowo) to Stargard-Massow (near Łęczyca) segment was built subsequently. Construction stopped in 1942, as military priorities once again took over available labour. In 1945, German forces, retreating along the Eastern Front, blew up most of the bridges to slow the Soviet advance.