The YubiKey is a hardware authentication device manufactured by Yubico to protect access to computers, networks, and online services that supports one-time passwords (OTP), public-key cryptography, authentication, and the Universal 2nd Factor (U2F) and FIDO2 protocols developed by the FIDO Alliance. It allows users to securely log into their accounts by emitting one-time passwords or using a FIDO-based public/private key pair generated by the device. YubiKey also allows storing static passwords for use at sites that do not support one-time passwords. Google, Amazon, Microsoft, Twitter, and Facebook use YubiKey devices to secure employee accounts as well as end-user accounts. Some password managers support YubiKey. Yubico also manufactures the Security Key, a similar lower-cost device with only FIDO2/WebAuthn and FIDO/U2F support.

The YubiKey implements the HMAC-based one-time password algorithm (HOTP) and the time-based one-time password algorithm (TOTP), and identifies itself as a keyboard that delivers the one-time password over the USB HID protocol. A YubiKey can also present itself as an OpenPGP card using 1024, 2048, 3072 and 4096-bit RSA (for key sizes over 2048 bits, GnuPG version 2.0 or higher is required) and elliptic curve cryptography (ECC) p256, p384 and more, depending on version, allowing users to sign, encrypt and decrypt messages without exposing the private keys to the outside world. Also supported is the PKCS#11 standard to emulate a PIV smart card. This feature allows code signing of Docker images as well as certificate-based authentication for Microsoft Active Directory and SSH.

Founded in 2007 by former CEO now Chief Evangelist Stina Ehrensvärd, Yubico is a Public company with offices in Santa Clara, CA, Bellevue, WA, and Stockholm, Sweden. Yubico CTO, Jakob Ehrensvärd, is the lead author of the original strong authentication specification that became known as Universal 2nd Factor (U2F).

YubiKey released the YubiKey 5 series in 2018, which adds support for FIDO2.

Yubico was founded in 2007 and began offering a Pilot Box for developers in November of that year. The original YubiKey product was shown at the annual RSA Conference in April 2008, and a more robust YubiKey II model was launched in 2009. Yubico's explanation of the name "YubiKey" is that it derives from the phrase "your ubiquitous key", and that "yubi" is the Japanese word for finger.

YubiKey II and later models have two "slots" available, for storing two distinct configurations with separate AES secrets and other settings. When authenticating, the first slot is used by only briefly pressing the button on the device, while the second slot gets used when holding the button for 2 to 5 seconds.

In 2010, Yubico began offering the YubiKey OATH and YubiKey RFID models. The YubiKey OATH added the ability to generate 6- and 8-character one-time passwords using protocols from the Initiative for Open Authentication (OATH), in addition to the 32-character passwords used by Yubico's own OTP authentication scheme. The YubiKey RFID model included the OATH capability plus also included a MIFARE Classic 1k radio-frequency identification chip, though that was a separate device within the package that could not be configured with the normal Yubico software over a USB connection.

Yubico announced the YubiKey Nano in February 2012, a miniaturized version of the standard YubiKey which was designed so it would fit almost entirely inside a USB port and only expose a small touch pad for the button. Most later models of the YubiKey have also been available in both standard and "nano" sizes.