The Porsche flat-six engine series is a line of mechanically similar, naturally aspirated and sometimes turbocharged, flat-six boxer engines, produced by Porsche for almost 60 consecutive years, since 1963.

[8][9] The engine is an evolution of the flat-four boxer used in the original Volkswagen Beetle.

[14][15][16][17] In April 2011, Porsche announced the third generation of the 997 GT3 RS with an enlarged 4.0-litre engine having a power output of 500 PS (368 kW; 493 hp).

[18][20] At 493 hp (368 kW),[21] the engine is one of the most powerful six-cylinder naturally aspirated engines in any production car with a 123.25 hp (92 kW) per litre output.

[26][27][28] The Porsche 962 sports prototype also used a twin-turbocharged flat-six engine.