Onterris, Inc. operates as an environmental services company in the United States, Australia, Canada, and internationally. It operates in two segments: Consulting and Treatment, and Measurement and Analysis. The Consulting and Treatment segment provides environmental consulting, engineering, and implementation services to help clients assess, manage, and mitigate environmental risks across the lifecycle of their operations and projects. It supports environmental assessments, regulatory permitting, toxicology consulting, emergency preparedness, and response and environmental audits and permits; and offers engineering, design, and implementation solutions to treat contaminated water and remediate soil. The Measurement and Analysis segment offers environmental testing and laboratory services. It tests and analyzes air, water, and soil to determine concentrations of contaminants, as well as the toxicological impact of contaminants on flora, fauna, and human health. This segment's offerings include source and ambient air testing and monitoring, and leak detection, as well as air, soil, stormwater, wastewater, and drinking water analysis. The company was formerly known as Montrose Environmental Group, Inc. and changed its name to Onterris, Inc. in April 2026. Onterris, Inc. was founded in 2012 and is headquartered in North Little Rock, Arkansas.