The American Society for the Prevention of Cruelty to Animals (ASPCA) is a non-profit organization which, as the name says, is dedicated to preventing cruelty towards animals. It was founded by Henry Bergh on April 10, 1866, in New York City. It is the oldest welfare organization in the United States. Their mission is "to provide effective means for the prevention of cruelty to animals throughout the United States."

The ASPCA works primarily with companion animal issues, such as pet care, equine or horse cruelty issues, and animal cruelty and neglect. Their programs and services include: a national poison control hotline for pet owners and animal health professionals; a shelter outreach program to promote best practices within locally-owned shelters, a corporate partner program to promote animal-friendly products and services, and a special anti-cruelty initiative to teach animal welfare education and animal welfare law enforcement practices (known as "humane law enforcement" within the organization) across the United States. In the state of New York, the ASPCA's Humane Law Enforcement division has powers to investigate cruelty and enforce laws. The Humane Law Enforcement division has been featured on the television program Animal Precinct.

Additionally, the ASPCA provides relief services for the domestic animal victims of natural disasters such as Hurricane Katrina, where the National Outreach department collected donations to provide supplies; coordinated volunteer efforts; deployed rescue teams to recover abandoned pets; provided temporary shelter to displaced animals; and reunited pets with their owners.

The ASPCA is very active in lobbying for animal welfare legislation, with regional and federal lobbyists covering all 50 states. The ASPCA communicates with federal and state legislators to consider animal-friendly legislation and bills. The ASPCA also drafts animal welfare legislation initiatives and proposals for legislators to consider during their sessions. The ASPCA's "Advocacy Brigade" allows users to write/e-mail their legislators on important animal legislation bills and referendums.