The Fiji mermaid was an object composed of the torso and head of a juvenile monkey sewn to the back half of a fish. It was a common feature of sideshows where it was presented as the mummified body of a creature that was supposedly half mammal and half fish, a version of a mermaid. The original had fish scales with animal hair superimposed on its body and pendulous breasts on its chest. The mouth was wide open with its teeth bared. The right hand was against the right cheek, and the left tucked under its lower left jaw. This mermaid was supposedly caught near the Fiji Islands in the South Pacific. Several replicas and variations have also been made and exhibited under similar names and pretexts. P. T. Barnum exhibited the original in Barnum's American Museum in New York in 1842, but it then disappeared—likely destroyed in one of the many fires that destroyed parts of Barnum's collections.

Barnum's American Museum was a dime museum located at the corner of Broadway, Park Row, and Ann Street in what is now the Financial District of Manhattan, New York City, from 1841 to 1865. The museum was owned by famous showman P. T. Barnum, who purchased Scudder's American Museum in 1841. The museum offered both strange and educational attractions and performances. Some were extremely reputable and historically or scientifically valuable, while others were less so.