An RSA certificate is a type of SSL/TLS certificate that uses the RSA encryption algorithm to secure data transmitted over the internet. RSA stands for Rivest Shamir Adleman, named after the inventors of the cryptographic algorithm. RSA certificates are used to establish a secure connection between a web server and a client and to verify the websites identity. They are commonly used in HTTPS, the secure version of the HTTP protocol used on the internet. RSA is a public-key encryption algorithm and is considered a standard for sensitive data encryption.

In addition to SSL/TLS certificates, RSA keys are also used for authentication and a symmetric key exchange during the establishment of an SSL/TLS session. RSA cryptography is based on the presumed difficulty of factoring large integers. A user of RSA cryptography creates and then publishes the product of two large prime numbers, along with an auxiliary value, as their public key. The prime factors must be kept secret. Anyone can use the public key to encrypt a message, but only someone with knowledge of the prime factors can feasibly decode the message.

RSA certificates are also used in software protection systems to ensure that only authorized users can access the protected software. Additionally, RSA personal certificates are used to sign and encrypt information in RSA tokens. In some regions, such as Queensland, Australia, RSA certification is required for staff of licensed premises who serve or supply alcohol.