The Opel Omega is an executive car engineered and manufactured by German automaker Opel between 1986 and 2003. The first generation, the Omega A (1986–1994), superseded the Opel Rekord. It was voted European Car of the Year for 1987, and was available as a saloon or estate. The second generation, the Omega B, was manufactured from 1994 to 2003.

Rebadged variants of the Omega were marketed worldwide, including in North America as the Cadillac Catera, in Great Britain as the Vauxhall Omega, and South America as the Chevrolet Omega. As with the Rekord which preceded it, re-engineered versions of the Omega were manufactured in Australia from 1988 as the Holden Commodore (and its derivatives) since 1999. Commodore-based cars were in turn exported to South America as the Chevrolet Omega and to the Middle East as the Chevrolet Lumina.

Production of the Omega was discontinued in 2003. It was succeeded by the Opel Signum.

The original Omega went into production in September 1986, as a replacement for the final version of the Opel Rekord, which had been in production since 1978. Sales began in November. The body was designed as an evolution of the previous Opel design theme engineered more towards aerodynamics in view of higher fuel prices and the general drive towards more fuel efficiency. The result was a remarkable drag coefficient of 0.28 (0.32 for the Caravan). The whole development program cost 2.5 billion Deutschmarks or £1.5 billion. The UK market version of the final generation of Rekord had been marketed as the Vauxhall Carlton, and this nameplate was retained for the new car.

Late in 1986, it was voted European Car of the Year for 1987, ahead of the highly acclaimed new versions of the Audi 80 and BMW 7 Series. Compared to the Rekord, the Omega featured many modern technological advances, which were new to Opel in general, if not to the volume segment European automotive market. These included electronic engine management, ABS, on-board computer (which displayed parameters such as momentary fuel consumption or average speed), air-conditioned glove compartment, and even the then fashionable LCD instrument cluster (available in CD version from 1987, but dropped in 1991). More importantly, the Omega came with a self-diagnosis system (which is now a standard feature in present-day cars), whose output could be read by appropriately equipped, authorised service stations. The Omega was one of the first cars to offer (individual) heated seats in the rear.

The Omega was sold in most European countries, albeit with "Vauxhall Carlton" badging in the United Kingdom. In Japan, the Omega A (and Vectra) were the first Opels to be distributed by Isuzu Motors Ltd. rather than by long-standing importer Toho Motors (東邦モーターズ), beginning in July 1989. In the Isuzu lineup, it was slotted above the Isuzu Aska.

All the Omega models used a longitudinally mounted engine with a rear-wheel drive setup, with a five-speed manual transmission or four-speed automatic transmission. The engine range consisted of 1.8 L, 2.0 L, and 2.4 L four-cylinder units (as well as 2.0 L, 2.3 L diesel, and 2.3 L turbodiesel) to 2.6 L, 3.0 L, and 3.0 L-24v six-cylinder units. The 1.8 L and 2.0 L four-cylinder petrol engines were all based on the Family II design, whilst the six-cylinder units and the 2.4 L four-cylinder were based on the older Opel cam-in-head engine family.

In Brazil, the car was sold as the Chevrolet Omega and powered by 2.0 L I4 (C20NE and C20YE) or 3.0 L I6 (C30NE) Opel engines until 1994. Since the discontinuation of the Omega A in Germany, General Motors do Brasil needed new engines to continue production and the 2.0 L I4 was replaced by 2.2 L I4 engine (C22NE) with 116 PS (85 kW; 114 hp) and 197 N⋅m (145 lb⋅ft). The 3.0 L I6 was replaced by the locally produced 4.1 L (250ci) Chevrolet Straight-6 engine (C41GE) with 168 PS (124 kW; 166 hp) and 285 N⋅m (210 lb⋅ft). As fitted to the Omega, this engine was tuned by Lotus and equipped with multi port fuel injection. The Chevrolet Omega was produced until 1998.