Jack Carroll "Jay" Haldeman II (December 18, 1941 – January 1, 2002) was an American biologist and science-fiction writer.
He was the older brother of SF writer and MIT writing professor Joe Haldeman.
Haldeman published at least 75 short stories, beginning with "Garden of Eden" in the magazine Fantastic (December 1971).
"High Steel", a 1982 story co-authored with Jack Dann, was a Nebula Award nominee; it was later expanded into a novel.
He was married to writer Barbara Delaplace; they collaborated on stories beginning with "That'll be the Day" in the anthology Alternate Tyrants.