In macroeconomics, hard currency, sound money, safe-haven currency, or strong currency is any globally traded currency that serves as a reliable and stable store of value. Factors contributing to a currency's hard status might include its historical use of as a money (such as gold or silver), or if it is a fiat currency, the stability and reliability of the respective state's legal and bureaucratic institutions, level of corruption, long-term stability of its purchasing power, the associated country's political and fiscal condition and outlook, and the policy posture of the issuing central bank.

Safe haven currency is defined as a currency which behaves like a hedge for a reference portfolio of risky assets conditional on movements in global risk aversion. Conversely, a weak or soft currency is one which is expected to fluctuate erratically or depreciate against other currencies. Softness is typically the result of weak legal institutions and/or political or fiscal instability. Junk currency is even less trusted than soft currency, and has a very low currency value. Soft and junk currencies often suffer sharp falls in value.

Throughout human civilization, gold and silver were used as hard currencies with the use of gold as money beginning at around 600 BCE in Asia Minor. In the early and high Middle Ages, the Byzantine gold solidus or bezant was used widely throughout Europe and the Mediterranean. Overtime, due to issues with divisibility, bimetallist standards emerged, with gold being used for large transactions and silver being used for small, day-to-day transactions. The adoption of bimetallism as internationally recognized hard currency developed rapidly when the ducat began to have a fixed value in terms of silver. The gold ducat originated in Venice in 1284 and gained international acceptance over the centuries.

With the rise of fiat currency, most notably from the 19th Century to the modern day, paper currencies of some developed countries have earned recognition as hard currencies at various times. These currencies have included United States dollar, euro, British pound sterling, Japanese yen, Swiss franc and to a lesser extent the Canadian dollar, Australian dollar, New Zealand dollar, Swedish krona, Singapore dollar, and Hong Kong dollar. As times change, a currency that is considered weak at one time may become stronger, or vice versa; the Japanese yen is a recent example.

Despite their countries' large economies, neither the Chinese renminbi (yuan) nor the Indian rupee are considered "hard" currencies. The rupee is not widely used in international trade and is not fully convertible on the capital account. In addition, India has a large trade deficit, which exerts downward pressure on the currency. The renminbi is not traded on world exchanges and the government places many controls on exchanging the currency.

One measure of hard currencies is how they are favored within the foreign-exchange reserves of countries:

The percental composition of currencies of official foreign exchange reserves from 1995 to 2025.

The US dollar (USD) has been considered a strong currency for much of its history. Despite the Nixon shock of 1971, and the United States' growing fiscal and trade deficits, most of the world's monetary systems have been tied to the US dollar due to the Bretton Woods system and dollarization. Countries have consequently been compelled to purchase dollars for their foreign exchange reserves, price their commodities in dollars for foreign trade, or even use dollars domestically, thus buoying the currency's value.