The ION was introduced in 2003 and represented Saturn's entry-level car, replacing the rather unimpressive Saturn S series sedan. This line of vehicles was marketed to younger drivers and their need for an affordably priced vehicle with a sporty style. There were two models available when this compact economy car was first introduced, a sedan and a Quad Coupe, which remains the case through the 2007 model year with all models being equipped with front wheel drive. The Quad Coupe is designed to appear like a two-door coupe but actually has two almost invisible rearward-opening doors similar in style to those popular on extended-cab pickup trucks. For the new line of sedan, the base model ION Sedan 1 was the lowest priced and was also essentially bare boned in terms of features in comparison to the amenities standard in other small cars- but it was also priced considerably lower. The ION Sedan 2 had a few more comfort and convenience features, and the ION Sedan 3 even more, but all the sedans were powered by the same strong yet fuel efficient 2.2 liter inline 4 cylinder engine.

In spite of the strong engine, the ION was labeled as lacking spirit, and performance was conservative. The overall low cost of the vehicle was most apparent in the lack of quality incorporated into the interior design. These complaints from both the automotive consumer population in addition to industry experts has prompted Saturn to make some much needed improvements throughout the years, although the vehicle itself is still only in its first generation it was quick to become a more viable competitor in the compact car marketplace. The 2004 saw improved interior components and fabrics and a recalibrated automatic transmission improved the timing at which gears would change and the engines response. The most significant changes thus far occurred for the 2005 models, which sported a new front fascia and exterior trim, and an acoustic engine cover in addition to other sound decreasing enhancements that considerably improved the noise level. In 2006, the ION 1 base model was dropped from the lineup, new wheels added a striking new exterior appearance and the ION 3 was available with a new Enhanced Performance Options package that included a 2.4 liter engine that delivered 170 horsepower and a sport tuned suspension.

Recent improvements have substantially improved the overall quality and driving experience associated with the Saturn ION sedan, though the seats are still rather uncomfortable and offer little support. However, the five years/100,000 miles powertrain warranty that was made available as of the 2007 model year ups the anty a bit and the ION is impressive enough, especially in handling sharp curves, and still affordable enough for younger drivers.