A private IP address is an IP address that is reserved for internal use behind a router or other Network Address Translation (NAT) device, separate from the public one. These are in contrast to public IP addresses, which are public and cannot be used within a home or corporate network. Sometimes a private address is also called a local IP address.

The Internet Assigned Numbers Authority (IANA) reserves the following IP address blocks for use as private IP addresses:

The first series contains over 16 million addresses, the second over 1 million and the last series over 65,000.

Another range of private IP addresses is 169.254.0.0 to 169.254.255.255, but these are only intended for Automatic Private IP Addressing (APIPA).