Gladys Porter Zoo is a zoological and botanical park located in Brownsville, Texas, United States. The zoo officially opened on September 3, 1971, and currently averages over 424,000 visitors annually. Situated on 31 acres (13 ha), the zoo houses about 400 animal species (including 47 endangered species) and over 250 tropical and neo-tropical species and subspecies. It is the first zoo to have successfully bred the endangered Jentink's duiker (although none are currently in captivity in the US). It is also the birthplace of Harambe, the gorilla.

The zoo is named after Gladys Porter, the daughter of Earl C. Sams, former president of J. C. Penney. Porter, a wildlife enthusiast, helped to plan and stock the zoo, which was entirely funded by the Earl C. Sams Foundation. After its opening, the zoo was given to the city of Brownsville.

The zoo was planned, built, stocked, and given by the Earl C. Sams Foundation to the City of Brownsville. It opened on 3 September 1971. The first addition to its exhibits was the Herpetarium, which opened in April 1973. The zoo has been the single largest recipient from the foundation funds established by Sams.

The zoo published the first issue of its Zoo News (its official newsletter and now a quarterly publication) in January 1972. The naturalistic exhibits at the zoo won the 1979 Texas Building Branch of Associated General Contractors Outstanding Construction Award.

In 1978, the zoo launched its summer study programs on a trial basis with classes for children in grades 1 through 12. Although only four classes were taught that summer, the program has expanded over the years and now includes classes in the spring and fall as well as summer. The zoo also received accreditation from the Association of Zoos and Aquariums (AZA) in 1978.

In subsequent years, Orangutan Island was enlarged, the Herpetarium was expanded with a new aquatic wing, and many other exhibits as well as facilities such as the gift shop, offices, and concession stands were remodeled or added. Most of these projects were made possible by the zoo's annual Zoofari fundraisers.

In 1986, the zoo created an endowment fund with the help of matching grants from the Earl C. Sams (dollar for dollar up to $2 million) and the Lightner Sams Foundation (dollar for dollar up to $1 million). Income from this permanent endowment now ensures that the zoo can maintain and improve itself.

The Australian exhibit opened in February 1988 — the largest addition to the zoo since its opening. The Education department was also expanded in 1989 and a walk-through aviary (Zack's Aerie, made possible by private donations) was also opened.

• Official website
• Handbook of Texas Online: Gladys Sams Porter
• Handbook of Texas Online: Gladys Porter Zoo