The Tatra 77 (T77) is one of the first serial-produced, truly aerodynamically-designed automobiles, produced by Czechoslovak company Tatra from 1934 to 1938. It was developed by Hans Ledwinka and Paul Jaray, the Zeppelin aerodynamic engineer. Launched in 1934, the Tatra 77 is a coach-built automobile, constructed on a platform chassis with a pressed box-section steel backbone rather than Tatra's trademark tubular chassis, and is powered by a 60 horsepower (45 kW) rear-mounted 2.97-litre air-cooled V8 engine, in later series increased to a 75 horsepower (56 kW) 3.4-litre engine. It possessed advanced engineering features, such as overhead valves, hemispherical combustion chambers, a dry sump, fully independent suspension, rear swing axles and extensive use of lightweight magnesium alloy for the engine, transmission, suspension and body. The average drag coefficient of a 1:5 model of a Tatra 77 was recorded as 0.2455. The later model T77a, introduced in 1935, has a top speed of over 150 km/h (93 mph) due to its advanced aerodynamic design which delivers an exceptionally low drag coefficient of 0.212. Sources claim that this is the coefficient of a 1:5 scale model, not of the car itself, so the actual drag coefficient may have been slightly higher.

The Tatra Company began manufacturing cars in 1897 in Kopřivnice, Moravia, in today's Czech Republic, making it the third-oldest still-existing automobile manufacturer in the world. Under the direction of Hans Ledwinka, the company employed many of the genius minds of automotive history, including Erich Übelacker and consultant Paul Jaray, who together designed the Tatra 77.

Paul Jaray first worked at Luftschiffbau Zeppelin (LZ) where he gained experience in the aerodynamic design of airships. He used his access to LZ's wind tunnels and subsequently established streamlining principles for car design. In 1927 he founded a company specializing in developing streamlined car bodies and selling issuing licences to major vehicle manufacturers. Tatra was the only manufacturer to incorporate Jaray's streamlining principles into their series car production, starting with the Tatra 77.

Before designing the large, luxurious T77, Jaray designed an aerodynamic body for the Tatra 57, a mid-range model. This prototype was not developed further and failed to reach production. Instead, Jaray constructed two prototypes for a concept designated the Tatra V570, which more closely conformed to his aerodynamic streamlining principles, featuring a beetle-shaped body.

However, at the time Tatra already had a cheap, strongly-selling car in its production range, which was moreover popular due to its continuation of the tradition of simplicity and ultra-reliability inaugurated by the Tatra 11. Although Tatra management saw the advantages of Jaray's concept, they believed that the new model would make sense only as an additional model with limited production, which meant that it should be aimed at the top of the automobile market. Ledwinka's team subsequently stopped work on the V570 and concentrated on designing large luxury cars. Tatra aimed to make state-of-the-art cars that would be fast, stable, nearly silent, economical and built to the most rigorous engineering standards, as well as reflect modern aerodynamic research.

The T77/77A cars were quite probably the last production use of the "walking-beam" valvetrain principle, their dry-sump air/oil-cooled V8 engines having overhead valves in hemispherical heads, but no pushrods. Instead the valves are opened by enormous drilled rockers operated by a single high camshaft between the two cylinder banks' heads, and pivoted inboard of their centres to extend the lift applied by the cams. The principle had been used much earlier in the Duesenberg 16-valve straight-4 low-twin-cam racing engine, later adopted by Rochester for use in passenger cars, but Tatra's use of a single camshaft to open the valves of a V8 without pushrods, rather than two low shafts on a straight engine, must be unique. A consequence is that the mechanical layout is much less obvious to the observer, with the big box-shaped engine giving few immediate clues to its V configuration, unlike its T87 OHC successor. Belt-driven squirrel fans in cast alloy ducting draw air forward, up and around the four shrouded pairs of finned iron cylinders, and a large hinged alloy cover maintains a warm environment for the carburettor in winter.

Hans Ledwinka was the chief designer responsible for the development of the new car, while Erich Übelacker was responsible for the body. Development was very secretive until the last moments of the official presentation on March 5, 1934, at Tatra's offices in Prague. The car was demonstrated on the road from Prague to Karlovy Vary, where it easily reached 145 kilometres per hour (90 mph), and amazed journalists with its great handling and comfortable ride at speeds of about 100 kilometres per hour (60 mph). On March 8, the Tatra was presented at Berlin motor show, where it became the centre of attention due not only to its atypical design but also to its performance. That same year the T77 was presented at the Paris motor show. There were even demonstration rides after doubt was cast on the ability of the car to reach 140 kilometres per hour (87 mph) with a mere 45 kilowatts (60 hp) of engine power: normally at that time twice the power was required for a car to reach such a speed. Director Maurice Elvey was so amazed by the looks of the car that he used the T77 in his science-fiction movie The Transatlantic Tunnel.

The Tatra 77 was an expensive luxury car – a price was 98,000 koruns (equal to some US$4,000 in 1935).