互联网安全协定（英语：Internet Protocol Security，缩写为IPsec），是一个协定组合，透过对IP协议的分组进行加密和认证来保护IP协议的网络传输协议族（一些相互关联的协议的集合）。

IPsec由两大部分组成：（1）创建安全分组流的密钥交换协议；（2）保护分组流的协议。前者为互联网密钥交换（IKE）协议。后者包括加密分组流的封装安全载荷协议（ESP协议）或认证头协议（AH协议）协议，用于保证数据的机密性、来源可靠性（认证）、无连接的完整性并提供抗重播服务。

Internet Protocol Security (IPsec) is a protocol suite for secure Internet Protocol (IP) communications by authenticating and encrypting each IP packet of a communication session. IPsec includes protocols for establishing mutual authentication between agents at the beginning of the session and negotiation of cryptographic keys to be used during the session. IPsec can be used in protecting data flows between a pair of hosts (host-to-host), between a pair of security gateways (network-to-network), or between a security gateway and a host (network-to-host). Internet Protocol security (IPsec) uses cryptographic security services to protect communications over Internet Protocol (IP) networks. IPsec supports network-level peer authentication, data origin authentication, data integrity, data confidentiality (encryption), and replay protection.