A moidore or moydore was historically a gold coin of Portuguese origin. While the coin shows a face value of 4,000 réis, its real value was 20% higher or 4,800 réis from 1688 to 1800. On its obverse is the face value and the Portuguese coat of arms, and on its reverse is the Order of Christ Cross. Moidores were minted from 1677 to as late as 1910, mainly in the Kingdom of Portugal and in Portuguese colonies like Brazil and Mozambique. Gold coins were also issued in fractions or multiples of moidores, ranging from one-tenth of a moidore to five moidores.

The real (meaning "royal", plural: réis or [archaic] reais) was the currency unit of Portugal from around 1430 until 1911, when the First Portuguese Republic introduced the escudo following the 1910 Republican Revolution.

Since the Portuguese empire (1415–1999) spread throughout a vast number of territories that are now part of 53 different sovereign states, moidores served as currency not only in those regions but also in other regions of the globe, including Western Europe and the West Indies.