The Hummer H3 is a sport utility vehicle/off-road vehicle from Hummer that was produced from 2005 to 2010. Introduced for the 2006 model year, it was based on a highly modified GMT355 underpinning the Chevrolet Colorado/GMC Canyon compact pickup trucks that were also built at GM’s Shreveport Operations in Shreveport, Louisiana and the Port Elizabeth plant in South Africa. The H3 was actually the smallest among the Hummer models. It was available either as a traditional midsize SUV or as a midsize pickup known as the H3T.

The H3 was launched with a 3.5 liter straight-5 cylinder L52 engine that produced 220 hp (160 kW) and 225 lbf⋅ft (305 N⋅m) of torque and was mated to a standard five-speed Aisin AR5 manual transmission or an optional Hydra-Matic 4L60-E four-speed automatic transmission. In 2007 this engine was replaced by the 3.7 liter LLR that produced 242 hp (180 kW) and 242 lbf⋅ft (328 N⋅m) of torque, figures that were revised in 2009 to 239 hp (178 kW) and 241 lbf⋅ft (327 N⋅m). Under revised EPA testing standards when equipped with either transmission this straight-5 engine achieved 14 mpg_‑US (17 l/100 km) in the city and 18 mpg_‑US (13 l/100 km) on the highway with a combined average of 15 mpg_‑US (16 l/100 km). Available solely with the automatic transmission, a 5.3 liter LH8 V8 engine producing 300 hp (220 kW) and 320 lbf⋅ft (430 N⋅m) of torque was added in 2008 for the Alpha model. The V8 version had lower fuel economy, estimated at 13 mpg_‑US (18 l/100 km) in the city, 16 mpg_‑US (15 l/100 km) on the highway, with a combined average of 14 mpg_‑US (17 l/100 km).