The Octopus card is a reusable contactless stored value smart card for making electronic payments in online or offline systems in Hong Kong. Launched in September 1997 to collect fares for the territory's mass transit system, it has grown into a widely used system for transport and other retail transactions in Hong Kong. It is also used for purposes such as recording school attendance and permitting building access. The cards are used by 98 percent of the population of Hong Kong aged 15 to 64 and the system handles more than 15 million transactions, worth over HK$220 million, every day.

Contactless payment systems are credit cards and debit cards, key fobs, smart cards, or other devices, including smartphones and other mobile devices, that use radio-frequency identification (RFID) or near-field communication (NFC) for making secure payments. The embedded integrated circuit chip and antenna enable consumers to wave their card, fob, or handheld device over a reader at the Point-of-sale terminal. Contactless payments are made in close physical proximity, unlike other types of mobile payments which use broad-area cellular or Wi-Fi networks and do not involve close physical proximity.