Constantine \c(o)-nsta-ntine, con-stan-tine\ as a boy's name (also used as girl's name Constantine), is pronounced KAHN-stan-teen. It is of Latin origin, and the meaning of Constantine is "constant, steadfast". From Constantinus, which is derived from Constans. The form Constant was popular among the Puritans as a virtue name. Constantine the Great, the fourth-century emperor, made Christianity the official state religion of the Roman Empire. Constantine was also the name of 11 Byzantine emperors, a royal name in Greece, and the name of three kings of medieval Scotland, where it is used as an anglicized form of Conn (Gaelic). The Russian czars, in a bid to legitimize Russia as the new home of Orthodoxy, also used the name.
For more information, see also the related name Costas.