Day One is a Maine nonprofit behavioral-health organization that provides substance-use and mental-health services for adolescents and families. The organization states that it has operated for more than 50 years and offers youth residential treatment, outpatient counseling, case management, psychiatric medication management, school-based services, and services for unhoused youth (Day One, Day One).

Day One describes its youth residential services as the only adolescent residential substance-use programs in Maine, with referrals coming from across the state. Maine's Office of Behavioral Health lists youth substance-use resources separately for children and adolescents, reflecting the state's distinct treatment and prevention system for youth substance use (Day One, Maine DHHS).

The organization is headquartered in Windham, Maine, and maintains public referral and contact information through its website (Day One).