zoo located in Brookfield, Illinois, U.S., a western suburb of Chicago. Brookfield Zoo, opened in 1934, is known for its extensive use of open-air, unbarred enclosures. It is owned by the Forest Preserve District of Cook County and is operated by the Chicago Zoological Society. Brookfield Zoo receives some 2 million visitors annually.

The 216-acre (87-hectare) zoo features Italian provincial buildings and formal malls. It has more than 2,500 specimens comprising some 425 different species. Special attractions include the dolphin shows in the Seven Seas exhibit (Brookfield was the first inland zoo to build a dolphinarium), a children's zoo, and Tropic World, a vast enclosed exhibit of mixed species from the three main rainforest habitats of the world (African, Asian, and South American). Other major exhibits are the Fragile Kingdom, depicting how animals relate to each other and their environment, and Habitat Africa, a two-part exhibit covering life in the rainforest and on the savanna. From 1937 to 1953 the zoo was home to three giant pandas: Su-lin (1937–38), Mei-mei (1938–42), and Mei-lan (1939–53). Brookfield has had exceptional success in breeding the sitatunga (a type of antelope); it also bred the world's first captive-born black rhinoceros (1941) and gray-headed kingfisher (1980), the first okapi born in the United States (1959), and the first wombat born outside Australia (1975). It has collections of hoofed stock, kangaroos, ibex, and baboons.