Big Brothers Big Sisters of America (BBBSA) is a charity organization which helps children develop to their full potential through the use of mentoring relationships with adults. Children who participate in Big Brothers Big Sisters of America are assigned a big brother or sister who agrees to serve as a mentor and role model, ideally for an extended period of time to create continuity for the child. In addition to operating extensively across the United States, the Big Brothers Big Sisters organization also works overseas.

According to records kept by Big Brothers Big Sisters of America, participants in the program are far less likely to drop out of school, start using drugs, or commit crimes. Children in Big Brothers Big Sisters of America programs also tend to be much more confident and outgoing, which gives them a greater chance at success in the world. Any child can join Big Brothers Big Sisters of America, although the program often includes a number of low-income and at-risk children, under the assumption that they are the most likely to benefit from supportive mentoring relationships.

The organization's roots can be found in the early 1900s, when mentoring organizations for young boys were established in several American cities, and became Big Brothers Big Sisters of America when Big Brothers of America and Big Sisters International merged in 1977. Today, Big Brothers Big Sisters of America is regarded as a premier charity, regularly earning high marks from organizations which monitor charities, and it is one of the foremost mentoring organizations in the United States.

Because of the obvious inherent risk in allowing unrelated adults to spend unsupervised time with children, Big Brothers Big Sisters of America is very careful to screen the adults who wish to participate as mentors in the program. When someone volunteers with Big Brothers Big Sisters of America, he or she is carefully interviewed, and the organization performs a background check and home inspection. The organization may also ask for proof of insurance and registration on any vehicles the child might ride in, and it requires impeccable references.

Mentors who participate in Big Brothers Big Sisters of America are incredibly varied. Some are professionals such as doctors, teachers, lawyers, and firefighters who hope to inspire the younger generation with their careers, but artists, tradesmen, and people in a wide variety of walks of life are welcome as well. The organization usually endeavors to make the best match possible between child and mentor, to promote a healthy and lasting friendship; some participants in Big Brothers Big Sisters of America continue to remain in contact after the little brother or sister comes of age, illustrating the powerful connection which can be created.