The Upper Occoquan Service Authority (UOSA) is a regional public utility in Northern Virginia, providing wastewater treatment and water reclamation services to Fairfax County, Prince William County, and the cities of Manassas and Manassas Park. Its advanced water reclamation plant has a treatment capacity of 54 million US gallons per day, with highly treated water returned to the Occoquan Reservoir, an important source of drinking water for the region.

UOSA is recognised for its pioneering approach to water reuse and watershed protection. Established in response to water quality challenges in the Occoquan watershed, it has helped protect the reservoir by replacing 11 smaller treatment plants with a single advanced regional facility. Today, it continues to advance treatment performance and resource efficiency, including through process innovations designed to unlock capacity within existing infrastructure and defer major capital investment.

On 28 September 2026, at WEFTEC in New Orleans, UOSA joined the Leading Utilities of the World network, represented by Brian Steglitz, Chief Executive Officer.