These older Ubuntu releases are now in Extended Maintenance (ESM):

We are happy to provide hosting for the following projects via the cdimage server. While they are not commercially supported by Canonical, they receive full support from their communities.

The cdimage server also hosts releases of other Ubuntu images not found on this server, such as builds for less popular architectures and other non-standard and unsupported images. For Ubuntu Desktop and Server on popular architectures, please see the links above instead.

Ports, Unsupported, and Experimental Images for Ubuntu

For old releases, see old-releases.ubuntu.com.