The Kia K5, formerly known as the Kia Optima, is a mid-size car manufactured by Kia since 2000 and marketed globally through various nameplates. First generation cars were mostly marketed as the Optima, although the Kia Magentis name was used in Europe and Canada when sales began there in 2002. For the second-generation models, Kia used the Kia Lotze and Kia K5 name for the South Korean market, and the Magentis name globally, except in the United States, Canada, Malaysia and the Middle East, where the Optima name was retained until the 2021 model year. The K5 name is used for all markets since the introduction of the fifth generation in 2019.

Kia Corporation is a South Korean multinational automobile manufacturer headquartered in Seoul, South Korea. It is South Korea's second largest automobile manufacturer, after its parent company, Hyundai Motor Company, with sales of over 2.8 million vehicles in 2019. As of 2015, Kia is owned by Hyundai, which holds a 33.88% stake valued at just over US$6 billion. Kia in turn is a minority owner of more than twenty Hyundai subsidiaries ranging from 4.9% up to 45.37%, totaling more than US$8.3 billion.