The Cambodian riel (KHR) has been issued into two distinct riels. The first was issued between 1953 and May 1975. In between 1975 and 1980, Cambodia had no monetary system. On March 20, 1980, a second currency, also termed "riel", has been issued. According to popular belief, the name of the currency came from the Mekong river fish called the riel, meaning "small fish" in Khmer. It is more plausible that the name was derived from the Mexican real- a high silver content used by Malay, Indian and Chinese merchants in mid-19th-century Cambodia.
In 1953, notes dual denominated in piastre and riel; the riel being at par with the piastre was issued by the Cambodia branch of the Institut d'Émission des États du Cambodge, du Laos et du Vietnam. Simultaneously, the two other Institut branches had similar arrangements with the kip in Laos and the đồng in South Vietnam. At first, the riel was subdivided into 100 centimes but changed to 100 sen (សេន) in 1959. In the initial years, the riel and piastre circulated together. The first riel banknotes were also denominated in piastres. Although printed, the Khmer Rouge banknotes were not released as the Khmer Rouge took control of the country, and money was abolished. They printed a series of colored banknotes in 1993 for limited use on territories they control. On April 1, 1980, after the Vietnamese invasion, the riel was re-established as Cambodia's national currency. The central government gave away the new money to the populace to encourage its use, having a severely disrupted economy.
Though the riel is still in circulation in Cambodia, it now only dominates in rural areas, where it would be tricky to break a $20 bill, and tourists won't find anyone who will take their U.S. money if it's torn or old. Foreign currencies, U.S. dollars (USD) in particular, are more prevalent in cities and international destinations. Businesses in cities are inclined to list prices in USD. In total, the country's economy is 90% dollarized, and even Cambodian visas have to be paid for in USD.
Cambodian ATMs dispense both the Cambodian riel and USD, but foreign travelers can only draw from their foreign accounts in USD. Usually, they obtain riel in change from transactions and try not to hold too much money in the Cambodian currency since it can be inconvenient to convert back into USD or another currency.