The YubiKey 5Ci FIPS is a hardware security key designed for multi-factor authentication in government and regulated organizations. The device is FIPS 140-2 validated (Overall Level 2, Physical Security Level 3) and manufactured in Sweden with programming completed in the USA. The security key features dual connectors with USB-C and Lightning interfaces, enabling authentication across multiple device types without requiring NFC. It supports multiple authentication protocols including FIDO2/WebAuthn for hardware-bound passkeys, FIDO U2F, Yubico OTP, OATH-TOTP, OATH-HOTP, Smart card (PIV), and OpenPGP. The device operates as a HID keyboard, CCID smart card, and FIDO HID device. It includes a secure element and supports 25 passkey slots, 32 OATH slots, and 24 PIV certificates. Cryptographic support includes RSA (up to 4096-bit), ECC (P-256, P-384), and modern curves including Ed25519 and X25519. Physical specifications include IP68 water and dust resistance, crush resistance up to 25 N·m, and rated for 100,000+ USB insertion cycles. The device requires no batteries or network connectivity and has a mean time between failure of 100+ years. It operates between 0°C to 40°C and can be stored between -20°C to 85°C. The YubiKey 5Ci FIPS is compatible with Windows, macOS, Chrome OS, Linux, Chrome, and Edge browsers. It works with Google and Microsoft accounts, identity access managers, and password managers.