The MT900 is a sports car built in the United States and the United Kingdom by Mosler. Three submodels have also been produced. The MT900R was a racing version of the MT900. The basic car was updated as the MT900S for 2005, with the MT900S Photon being its racing variant. The original MT900 was introduced in 2001 and the MT900S continues in production. Components for 25 MTs were produced as of January, 2005, though only three road cars and eleven racing versions have officially been completed. The MT900 was the replacement for the Mosler Raptor.
The MT900 was designed by Rod Trenne, who previously worked on the Corvette C5. The name stood for Mosler, Trenne, and the car's 900 kilogram (1984 lb) target weight.
The MT900 used a carbon-fiber chassis with a LS1 V8 engine mounted amidships, powering the rear wheels. Power output is 350 hp (261 kW), with 350 ft·lbf (475 N·m) of torque. A ZF transaxle, designed for Porsche, was mounted upside down to allow the engine to sit in front of the rear axle.
The original MT900 weighed 1175 kg (2590 lb), much more than the target weight, but could still accelerate to 60 mph (97 km/h) in 3.5 seconds according to Car and Driver. The MT900 they tested could also do a 12.0 second quarter mile at 118 mph (190 km/h), and they recorded a top speed of 150 mph (241 km/h), limited by the redline. More impressive, the MT900 pulled 1.02 g on the skidpad. The EPA estimated 19 and 28 mpg (12.4 and 8.4 L/100 km) in city and highway driving, respectively.
The car had a somewhat plain exterior designed for aerodynamics, with a low 0.25 coefficient of drag. List price was US$164,000. Sales were certainly slow, however, with some reports even indicating that not a single road version of the MT900 was sold, with only a single prototype produced.
Introduced at the same time as the basic MT900 was the race-ready MT900R. It was designed for use in various international motorsports series for an estimated price of $119,000. The MT900R made its competition debut at the 2001 24 Hours of Daytona, and would be campaigned by a factory Mosler team for the full season of the Grand American Road Racing Championship. The entry finished the year ninth in their class championship.
For 2002, the French Perspective Racing team would become the full-season entry in Grand American and saw an improvement in performance. At Daytona the MT900R finished 13th overall and fifth in their class before winning at the next round at Homestead-Miami Speedway, helping the team to third in the championship. Rollcentre Racing and Balfe Motorsport (with aid from Rollcentre) would bring the Moslers to Europe in 2003, starting the British GT Championship year strong with three straight one-two finishes, before finishing the year with four more victories. The Rollcentre squad edged out Bafle for the championship that year. In Grand American, the Moslers were moved to the faster GTS class, but Perspective Racing improved on the previous year's Daytona effort with a ninth place finish and the class victory. Mosler Automotive would take one more victory that season.
Rollcentre and Balfe would continue in the British GT Championship in 2004, although Balfe would also enter the Spanish GT Championship. The Moslers would struggle in British GT and score no wins, but Balfe was able to earn two victories in Spanish GT, winning the drivers' championship by a mere point. 2005 would see Balfe entering the FIA GT Championship, although the car was not homologated and could not fight for points. Rollcentre would go on to win the Britcar 24 hours at Silverstone. Escuderia Bengala and Escuderia Motor Terrasa would compete in Spanish GT, while Eclipse Motorsport and Cadena GTC took over British GT competition.
The MT900 underwent several changes to become the MT900S. It now boasts 435 hp (324 kW) from its Corvette Z06-derived LS6 V8. The car weighs just 2200 lb (998 kg) without fuel.
An early prototype MT900S, despite being up 390 lb (177 kg) and down 65 hp (48 kW) from the production version, boasted a 0-60 time of 3.5 seconds and a quarter-mile time of 12 seconds flat.
A newer edition featuring 600 bhp prestated 0-60 mph in 3.1 seconds in Car & Drivers test in early 2006.

In June, 2005, Mosler announced that they had reached EPA and CARB certification on the MT900S, finally allowing road car sales to begin in the United States. The price is set at $189,000 with two examples having been built as of January 2005. George Lucas took delivery of the first street-legal MT900S in December 2006.