The Porsche 996 is the company's internal name for the version of the Porsche 911 model manufactured and sold between 1998 and 2005. It has since been replaced by the Type 997. Both body styles were used in 2005, depending on model. At its debut, it featured the most significant changes to the Carrera model since its introduction in 1963. The most important among these is the fully water-cooled engine, replacing the previously air-cooled engines used exclusively by the Carrera models. More stringent noise regulations and higher customer expectations for both refinement and a higher performance 4 valve per cylinder engine made the switch necessary. The 996 Carrera (not GT2, GT3 and Turbo models) engine is designed with what Porsche calls "integrated dry sump oiling". This "integrated dry sump" engine does not have an oil scavenge pump in the crankcase to pump the engine oil to a separate holding tank outside the crankcase as a true dry sump design would have. The only scavenge pumps in the 996 engine are in the camshaft boxes and the oil is pumped from there to the bottom of the crankcase as it would be in any "wet sump" engine.

Early 996 models had rare catastrophic engine failures which Porsche fixed discreetly under warranty by simply replacing complete engines. Other changes include a sleeker body with a more steeply raked windshield and a re-designed interior. The engines in the 1999 and 2000 version have a high failure rate due to a design error. Porsche North America will not admit to this problem nor will they provide any assistance in repairing this design flaw. Their only suggestion is for the owner to replace the engine out of pocket. This problem was supposedly fixed in mid 2000. One will notice the resale price difference with these model years and most of these models will have a new engine.

With these differences in mind, many "purists" consider the 996 to be an altogether different car since it is not air-cooled like the 993 and its predecessors all the way to the 356, at least in spirit, than the Carreras that preceded it, as opposed to being a development of the original.

The first 996s were available as a coupe or cabriolet with either rear wheel or all wheel drive and a 3.4 litre flat-6 normally aspirated engine producing 300 bhp (224 kW). These cars had the same front end as the 1996 Porsche Boxster. The design for the "fried egg" headlamp could be traced all the way back to the Porsche Panamericana concept car. In 2000, Porsche debuted the 996 Turbo, equipped with four-wheel-drive and a 3.6 litre, twin turbocharged and intercooled flat six producing 415 bhp (309 kW), making the car capable of 3.9 second 0 to 60 mph times. An "X50" upgrade package was available from the factory in 2002, increasing power to 444 hp (336 kW) through minor revisions to the turbochargers and engine control software.

Porsche produced a Turbo "S" in 2005, featuring the X50 engine upgrades and the formerly optional ceramic brakes as standard equipment. In 2002, the standard models underwent minor re-styling, which included switching to the Turbo-style headlamps and to a new front fascia. These were sometimes known as the Mk.II generation of the 996. In addition, engine capacity was also increased to 3.6 litres across the range, yielding gains of 20 horsepower (15 kW) for the non-Turbo models. 2002 also marked the start of the production of the 996 based Targa, featuring a sliding glass "green house" roof system like its Type 993 predecessor.

GT variants
Like the 993 before it, the 996 platform was used as the basis for two lightweight GT variants called GT2[1] and GT3. The GT3 was based on the standard RWD 996 Carrera, but was stripped of a great deal of equipment for weight savings, featured stiffer, adjustable suspension and upgraded brakes, and used the bodyshell of the four-wheel-drive version, which incorporated additional front-end stiffening. It was produced in two versions. The first, commonly referred to as the Mk.I GT3, was released in 1999 in all markets, save North America. It featured a naturally aspirated version 3.6L flat six making 360 bhp (270 kW). This engine was shared with the 996 Turbo and was a derivative of the Le Mans winning engine developed for the 911 GT1.