Mermaid Man and Barnacle Boy are a duo of fictional characters from the American animated television series, SpongeBob SquarePants. They were respectively voiced by guest stars Ernest Borgnine and Tim Conway, who both previously starred in the 1960s sitcom McHale's Navy. Mermaid Man and Barnacle Boy first appeared in the eponymous season one episode that premiered on August 21, 1999, and have since been featured as recurring characters. Following the actors' deaths, the characters have been relegated to non-speaking cameos after creator Stephen Hillenburg requested not to recast the characters.

Ernest Borgnine was an American actor whose career spanned over six decades. He was noted for his gruff but relaxed voice and gap-toothed Cheshire Cat grin. A popular performer, he also appeared as a guest on numerous talk shows and as a panelist on several game shows.