Jack C. Haldeman II (1941–2002) was an American biologist and science fiction author known for blending scientific expertise with imaginative storytelling. He published over 100 short stories and several novels, including Vector Analysis and Perry’s Planet, a Star Trek tie-in. His work often featured sports themes and alternate history, and he co-authored with writers like Joe Haldeman, Jack Dann, and Harry Harrison. A dedicated member of the sci-fi community, he chaired conventions and contributed to fandom culture. His scientific background included research in parasitology, whale studies, and the greenhouse effect.