Humphrey the Whale is a humpback whale that twice deviated from his Mexico to Alaska migration by entering San Francisco Bay. This behavior is unusual for a humpback whale, and Humphrey attracted wide media attention when entering the bay in both 1985 and 1990. Both of his bay incursions resulted in rescue by the Marine Mammal Center, based in Marin County, California, assisted by the United States Coast Guard and hundreds of other volunteers.

The Marine Mammal Center (TMMC) is a private, non-profit U.S. organization that was established in 1975 for the purpose of rescuing, rehabilitating and releasing marine mammals who are injured, ill or abandoned. It was founded in Sausalito, California, by Lloyd Smalley, Pat Arrigoni and Paul Maxwell. Since 1975, TMMC has rescued over 24,000 marine mammals. It also serves as a center for environmental research and education regarding marine mammals, namely cetaceans, pinnipeds, otters and sirenians. Marine mammal abandonment refers to maternal separation; pups that have been separated from their mother before weaning. At the center, they receive specialized veterinary care: they are diagnosed, treated, rehabilitated and ideally, released back into the wild. Animals in need of assistance are usually identified by a member of the public who has contacted the center. These animals represent the following major species: California sea lions, northern elephant seals, Pacific harbor seals, northern fur seals, Guadalupe fur seals, Hawaiian monk seals, and southern sea otters. On a few occasions, TMMC has taken in Steller sea lions and bottlenose/Pacific white-sided dolphins. The only non-mammals that TMMC takes in are sea turtles.