The Illinois State Toll Highway Authority (ISTHA) is an administrative agency of the U.S. state of Illinois charged with building, operating, and maintaining toll roads in the state. The roads, as well as the authority itself, are sometimes referred to as the Illinois Tollway. The system opened in 1958 in the Chicago area, and has subsequently expanded to include the eastern and central sections of Interstate 88 (I-88) extending into the northwestern part of the state. Beginning in 2005, the system was reconstructed to include more lanes and open road tolling, the latter of which uses I-Pass transponders to collect revenue as vehicles pass antennas at toll plazas or designated entrance or exit ramps. As of 2017, ISTHA maintains and operates 294 miles (473 km) of tollways in 12 counties in Northern Illinois.

A toll road, also known as a turnpike or tollway, is a public or private road for which a fee is assessed for passage. It is a form of road pricing typically implemented to help recoup the costs of road construction and maintenance.