Big Brothers Big Sisters of America is a 501(c)(3) non-profit organization whose mission is to "create and support one-to-one mentoring relationships that ignite the power and promise of youth". Adult volunteers are matched with children from age 5 to young adulthood. It was founded by Ernest Kent Coulter.

As one of the oldest and largest youth mentoring organizations in the United States, BBBSA provides guidance, resources, and support to its network of local BBBS agencies.

Local BBBS agencies operate under the umbrella of BBBSA, implementing mentoring programs in their respective communities. These agencies match adult volunteers (Bigs) with children (Littles) ages 5 through young adulthood. The specific age range of children and youth served may vary by affiliate.

The mentoring programs offered by local BBBS agencies are designed to help children reach their full potential and thrive in various aspects of their lives, including education, social skills, and personal development.

The group holds a congressional charter under Title 36 of the United States Code.

Public/Private Ventures, an independent Philadelphia-based national research organization, conducted a study from 1994 to 1995, monitoring 950 boys and girls nationwide to study the effects of Big Brothers Big Sisters. CEO Karen J. Mathis reported that the study found favorable outcomes to the organization.

Public/Private Ventures conducted another study in 2011 that evaluated the school-based Big Brothers Big Sisters Program. This program also found favorable outcomes.

In 2025, Big Brothers Big Sisters of America released a comprehensive study conducted in collaboration with researchers from Harvard University and the U.S. Department of Treasury, examining the long-term effects of their mentorship programs. The study, which analyzed three decades of data, demonstrated significant positive outcomes across educational, economic, and social dimensions.