The Diamond DA42 Twin Star is a four seat, twin engine, propeller-driven airplane manufactured by Diamond Aircraft Industries. Its airframe is made largely of composite materials.

The DA42 Twin Star was certified in Europe in 2004 and in the United States in 2005.
The airplane is made of carbon composite material. It is equipped with a Garmin G1000 glass cockpit.

The DA42 Twin Star was the first diesel-powered fixed-wing aircraft to make a non-stop crossing of the North Atlantic, in 12.5 hours, with an average fuel consumption of 5.74 gallons per hour (2.87 gallons per hour per engine).
In June 2010 a DA42 powered by Austro AE300 engines became the first aircraft to be publicly flown on algae-derived jet fuel.

The DA42NG "New Generation" is powered by Diamond's 3rd Generation Austro Turbo Diesel Engine, the Lycoming IO-360 engine is also available as an option. The 125 kW (168 hp) Austro diesel replaces the Thielert Centurion 1.7 and 2.0 engines. It is known for its good fuel efficiency, it uses 3.2 gallons per hour while loitering at maximum endurance or 8 gallons per hour at maximum continuous power (92%). It is also available with optional "on top" exhaust mufflers that reduce noise levels to below 59 decibels at 500 feet.

Thielert Aircraft Engines ended its production of the 1.7 litre Centurion engines (designated as TAE 125-01 Centurion 1.7) in favour of a new 2.0 litre. (TAE 125-02-99) engine. Diamond began installing this new 2.0 L. engine in early 2007. Although engine displacement increased, it was de-rated to produce the same horsepower (135) and torque (302 ft·lbf.) as the 1.7 L. engine.