Bill Chalker is an Australian UFO researcher and author who has investigated reports of unusual aerial phenomena in his country since the 1970s. Born in Grafton, New South Wales, in 1952, he studied chemistry and mathematics at the University of New England and has worked in the food industry since 1975 as an industrial chemist, laboratory manager and quality manager. Alongside that career he coordinates the Sydney-based UFO Investigation Centre and has specialised in physical-trace cases, in which witnesses report marks or residues left on the ground.

Chalker served as New South Wales representative of the Mutual UFO Network from 1976 to 1993 and as Australian representative of the Aerial Phenomena Research Organisation from 1978 to 1986, and he is a contributing editor of the International UFO Reporter, the journal of the Center for UFO Studies. In January 1982, after about a year of telephoning the Department of Defence, he spent a week at the Russell Offices in Canberra reviewing the Royal Australian Air Force's files on unusual aerial sightings. ABC News reported that staff stamped the pages "declassified" on his first morning. Among the files he found a reference to a 1954 report the air force had commissioned from physicist Harry Turner, and he concluded that an October 1973 sighting at the North West Cape communications base, which he already knew of, had been removed.

His books are The Oz Files: The Australian UFO Story (Duffy and Snellgrove, 1996) and Hair of the Alien: DNA and Other Forensic Evidence for Alien Abductions (Paraview Pocket Books, 2005), a study of forensic genetics in reported abductions that includes an interview with the experiencer Peter Khoury. He wrote the Australian chapter of the UFO History Group's UFOs and Government (2012) and the Australian entries for later editions of Jerome Clark's The UFO Encyclopedia. His retrospective field investigations include Willow Grove (1963) and three cases from 1966: Tully, Westall and Burkes Flat.

Several of those cases reached their 60th anniversaries in 2026. Chalker first waded through Horseshoe Lagoon, site of the January 1966 Tully saucer nest, in the early 1970s and spoke with the farmer George Pedley over the years; in August 2026 he lectured on the case at the Australian UFO Festival in nearby Cardwell, rejecting waterspout and wind-vortex explanations and calling it "a UFO physical trace case." In June researcher Grant Lavac released Chalker's unedited 2006 interviews with witnesses to the Westall encounter, recorded at the 40th-anniversary reunion.

Chalker also interviewed Turner at length before his death and received much of his personal files. When a 1971 Joint Intelligence Organisation paper by Turner circulated in the American disclosure debate, referenced by David Grusch, Jesse Michels and others, Chalker told Lavac it was a draft that never became a formal document: "It was never an official view. It was Harry's view." He added that it does not refer to crashed craft. Four decades of archival work and his custody of Turner's papers have made him a standard point of reference whenever Australian cases resurface overseas.