Arthur Leigh Allen, born in 1933, lived a life that included service in the U.S. Navy, a career as a teacher and mechanic, and significant legal entanglements, including a conviction for child molestation. He is primarily known for being the central figure of suspicion in the unsolved Zodiac Killer investigations that spanned decades. Allen was interviewed multiple times by law enforcement and was the subject of numerous search warrants throughout his life. Despite various pieces of evidence and witness testimonies connecting him to the crimes, definitive proof remained elusive, and some evidence also served to exclude him. He died in 1992.

Born in Honolulu, Hawaii, in 1933, Arthur Leigh Allen spent his formative years in Vallejo, California. He served in the U.S. Navy from 1951 to 1959, earning the China Service Medal for his time in Southeast Asia. While serving, he was court-martialed for bringing a firearm onto a naval base but was acquitted. Following his military service, Allen attended California Polytechnic State College, where he excelled as a collegiate trampoline champion in 1959. He later moved to Atascadero, California, pursuing careers as a teacher and a mechanic.

Allen became a person of interest in the Zodiac Killer investigation early on, with police focusing on him for over twenty years. During this period, he was interviewed numerous times and was the subject of several search warrants. While some investigators and individuals, including author Robert Graysmith and former SFPD investigator Dave Toschi, considered him the most likely suspect, other evidence later cast doubt on his involvement. For instance, testimony from a police officer who may have seen the killer fleeing a crime scene described a man significantly different in build from Allen. Furthermore, DNA evidence extracted from Zodiac letters did not match Allen's profile. However, a witness did identify Allen from a photo lineup as the man who shot him in 1969, and a Royal typewriter seized from his residence matched the type used in one of the Zodiac's letters. He also owned a watch with a logo similar to the killer's symbol.

Allen's life was significantly impacted by legal issues, notably an arrest in 1974 for lewdness with a minor. He pleaded guilty, leading to evaluation and treatment at Atascadero State Hospital and a subsequent suspended prison sentence with probation, which he successfully completed. This period coincided with the cessation of the Zodiac's communications, though a possible letter was received after Allen's release. Further complicating the case, former associates made allegations suggesting Allen's guilt. One friend reported that Allen had spoken of killing people and used the name 'Zodiac.' More disturbingly, in a 2024 documentary, acquaintances claimed Allen confessed to being the Zodiac before his death, and one recounted him molesting her and admitting to drugging her and Connie, another child, before allegedly confessing to being the Zodiac. Allen also made statements about a potential victim named 'Connie Henly' that some believe were connected to Connie Seawater, a childhood friend's daughter.