The Toyota Mark X (Japanese: トヨタ・マークX, Toyota Māku X) is a mid-size car manufactured by Toyota between 2004 and 2019, and was primarily aimed at the Japanese market. In Japan, it was the top-level car, sold only new at Toyopet Store locations. The Mark X was introduced in 2004 and is the successor to the Mark II which was first introduced in 1968, and was known in the North American market as the Corona Mark II starting in 1972, and renamed the Cressida from 1977 to 1992.

The "Mark X" is not pronounced "Mark Ten" but "Mark Ex", though the "Mark II" is "Mark Two". The Mark X is a continuation of the previous Mark II and its siblings, the sport-oriented Chaser, and the luxurious Cresta in one vehicle, repeating an approach previously attempted by the short-lived Verossa that used inline-six engines, whereas the Mark X uses V6 engines.

The Mark X was previously sold as an alternative to the front-wheel drive Camry, which was once the largest new saloon at Corolla Store locations, for buyers who like the size of the Camry, but prefer a rear-wheel drive layout.

Different engine sizes were offered to allow Japanese buyers which annual road tax they were willing to pay; the larger engines offer higher levels of standard equipment and luxury features. Both the first and second generation Mark X were manufactured at the Motomachi plant in Japan.

The Mark X was sold as the Reiz (Chinese: 锐志; pinyin: Ruìzhì) in China, which was produced by Tianjin FAW Toyota Motor Co. Ltd. It was produced until 2017. The Mark X was also officially imported to Indonesia in limited quantities between 2012 and 2013, to replace Australian-built Camrys as premium taxis.