A leased line is a permanent fiber optic or telephone connection between two points set up by a telecommunications carrier. A leased line is also sometimes referred to as a dedicated line. They can be used for telephone, data, or Internet services. Oftentimes businesses will use a leased line to connect to geographically distant offices because it guarantees bandwidth for network traffic. For example, a bank may use a leased line in order to easily transfer financial information from one office to another. A leased line can span long or short distances and customers generally pay a flat monthly rate for the service depending on the distance between the two points.

Leased lines do not have telephone numbers because each side of the line is always connected to one another, as opposed to telephone lines which reuse the same lines for numerous conversations through a process called "switching." The information sent through the leased line travels along dedicated secure channels, eliminating the congestion that occurs in shared networks. Connection speeds can range from 64 kbps (kilobits per second) to 45 mbps (megabits per second)and the bandwidth required is dictated by the quantity of data that will be sent and received.

Some individuals are also starting to use leased lines in order to obtain a faster, more reliable Internet connection. They also may save an individual money if he/she happens to spend a significantly large amount of time on the Internet. While most leased lines cost about $1,000/month, there are lines called Fractional T1 lines which start at 128 kbps and are less expensive. Installation is the same as for ordinary telephone lines.

Leased lines were used before the advent of the Internet and were actually utilized in 1950 by Project RAND (Research and Development) when collaborating across the country from Pennsylvania to California.

Some of the benefits of a leased line over other telephone and Internet connections are: faster download and upload speeds, a wide choice of bandwidths, guaranteed bandwidth for business usage, and suitability for web hosting.