So, it’s a complicated subject, because it depends on the definition of “crypto currency”, primarily the currency part of the term.

Technically, “crypto” as meaning cryptography, as we commonly use it today, as a form of “money”was implemented in 1995 as digicash, an implementation of the e-cash thesis.

There were other attempts such as b-money and a described bitgold, but none of them implemented the proof of work methodology as invented by Satoshi, and therefor were not successful as a form of “currency.”

As such, some consider bitcoin the first true “cryptocurrency.”

The term had grown to include all kinds of digital tokens that use cryptography, but I’d suggest bitcoin is the one and only.