Ráj (Polish: Raj, German: Roj) is a district of the city of Karviná in Karviná District, Moravian-Silesian Region, Czech Republic. It was a separate municipality but in 1948 became administratively a part of the city of Karviná. It lies in the historical region of Cieszyn Silesia and has a population of 17,142 (2001).
The hospital is located there, as well as the football field, home of the local team MFK Karviná.
The name is cultural in origin, literally paradise, fertile and beautiful land.
The settlement was first mentioned in a Latin document of Diocese of Wrocław called Liber fundationis episcopatus Vratislaviensis from around 1305 as item Frienstad in Ray. It meant that the village served as the foundation ground for Fryštát (Frienstad), and as such it had to be much older.
Politically the village belonged initially to the Duchy of Teschen, formed in 1290 in the process of feudal fragmentation of Poland and was ruled by a local branch of Silesian Piast dynasty. In 1327 the duchy became a fee of the Kingdom of Bohemia, which after 1526 became a part of the Habsburg Monarchy.
After the Revolutions of 1848 in the Austrian Empire, a modern municipal division was introduced in the re-established Austrian Silesia. The village as a municipality was subscribed to political district and legal district of Freistadt.