The Isuzu Trooper is a mid-size SUV produced by the Japanese automaker Isuzu between 1981 and 2002. It was exported worldwide as the Isuzu Bighorn, Subaru Bighorn, Isuzu Trooper, Honda Horizon, Acura SLX, Chevrolet Trooper, Opel/Vauxhall Monterey, Holden Jackaroo and Holden Monterey. It was a huge seller in the sport utility vehicle segment.

There were two generations of the Trooper produced – the first spanning 1981 through 1991, and the second from 1992 through 2002 when Isuzu ceased export of the model. It began its production run being somewhat primitive and underpowered, offered only with a 4 cylinder motor, standard 5 speed manual transmission, and part-time four-wheel drive system. As the first generation progressed, it became more luxurious, and offered more amenities, including a V6 engine. The second generation was more refined, and was available with two-wheel drive.

The Opel Monterey was a Japanese-built four-wheel drive Sports Utility Vehicle produced by General Motors. It was visually identical to the Isuzu trooper, but was only sold in Europe. Production began in 1994, with versions sold on Mainland Europe wearing Opel badges, and the British version being sold as a Vauxhall. Sales in Britain were disappointing, and the Vauxhall version of the car was withdrawn from sale at the end of 1998, though the Opel version continued to sell on the continent until 2002.

The first generation Trooper was available as a 2 or 4 door, with a solid rear axle and the front featuring independent suspension. Early engines included 2.0L 1.9L and a 2.2L diesel which many consider underpowered for the vehicle's weight—about 3,700lb (1,678.3kg) empty. The four-wheel drive system required the driver to engage the front axle by operating a three-position shifter adjacent to the regular transmission shifter. Both Aisin manual-locking and Isuzu's own auto-locking hubs were available. In 1986, Isuzu introduced a 2.3L engine, which, though only 112hp (102kW), was a vast improvement over the previous engines. In 1987 Isuzu introduced its first fuel-injected engine,(v tech injection) a 2.6L (4ZE1), for the Trooper. Some U.S. models were equipped with a GM 2.8L V6 engine (same powerplant found in the Chevrolet S10 pickup. Manual transmission equipped models had a gear driven transfer case with a 2.28:1 low range ratio, models equipped with the 2.6L four-cylinder engine and automatic transmission had a 2.66:1 low range transfer case. As foreign SUVs gained market share, tariffs were introduced, and Isuzu for a time imported a model known as the Trooper II. In a bit of a creative loophole jumping, Isuzu avoided the tariffs by having the dealers install the rear seats. Later first-generation models included an option for a four-speed automatic transmission, a V6 engine sourced from General Motors (their 2.8L pushrod V6), and a combination of 31"x10.5" tires with 4.77:1 differential gears. Standard differential gearing for all 1981-1991 Isuzu Trooper is 4.555:1. Models from 1988-1991 are equipped with Isuzu 10-bolt 17-spline front IFS differentials and Isuzu 12-bolt live rear axles with 4-wheel disc brakes. Also new for 1987 were new rectangular headlights, a departure from the earlier round sealed-beam type lights. A clutch-type limited slip rear differential was available as an option, indicated by the code "G80" on the vehicle's option plate under the hood. Overseas model engines not released in the United States included the Isuzu 4JB1 and 4JB1-T engines, (2.8L diesel inline four-cylinder engines, the "-T" indicating a turbocharged version).