A proximity card or prox card[1] is a "contactless" smart card which can be read without inserting it into a reader device, as required by earlier magnetic stripe cards such as credit cards and "contact" type smart cards.[2] The proximity cards are part of the Contactless card technologies. Held near an electronic reader for a moment they enable the identification of an encoded number. The reader usually produces a beep or other sound to indicate the card has been read. Proximity cards typically have a read range up to 50 cm (> 15 inches)[1] which is the main difference with contactless smartcard with 2 to 10 cm (1 to 3 inches) . The card can often be left in a wallet or purse[citation needed], and read by simply holding the wallet or purse near the reader. The term "proximity card" refers to the older 125 kHz devices in opposition to the newer 13.56 MHz contactless smartcards.

Proximity cards can't hold more data than a magnetic stripe card. Only contactless smartcards can hold other type of data like electronic funds balance for contactless payment systems, history data for Time & Attendance or biometric templates. When used without encoding data, only with the Card Serial number, contactless smartcard have similar functionalities with Proximity cards.