(image courtesy of Wikimedia Commons)
Budd Hopkins (mostly art related, but has manuscript for one of his UFO books – Smithsonian)
https://www.aaa.si.edu/collections/april-kingsley-and-budd-hopkins-papers-7799
Otto Binder papers – Texas A&M (sci fi author who wrote extensively on UFOs)
https://findingaids.library.tamu.edu/index.php/otto-binder-collection
Gray Barker (UFO writer, founder of The Saucerian magazine, and hoaxer)
https://s8853670.stacksdiscovery.com/gray-barker-ufo-collection
Paul R. Hill Collection, 1936-1996 (renowned NASA engineer and UFO enthusiast)
https://ead.lib.virginia.edu/vivaxtf/view?docId=vt/viblbv00742.xml
Ted Bloecher papers 1950-2000 (retired actor and member of the New York City Gay Men's Chorus, former officer of NICAP, and 30 year career researching UFOs)
https://archives.nypl.org/mss/5984
Jack D. Pickett papers, 1950s-2006 (UFO researcher and expert on experimental and unconventional military aircraft)
Leon Davidson's flying saucer collection, 1950-1980 (UFO researcher for USAF)
https://findingaids.library.columbia.edu/ead/nnc-rb/ldpd_4079689
Roy Craig Collection on the Scientific Study of Unidentified Flying Objects: 1963-ca. 2002 (chief field investigator for the Condon Committee report)
Chester C. Grusinski papers, 1952-1994 (Naval officer’s personal documents regarding UFO incident in Guantanamo Bay, Cuba 1958)
Arthur Bray papers (Canadian UFO Researcher and writer)
https://biblio.uottawa.ca/atom/index.php/arthur-bray
Wilbert Smith papers (wholly contained in Arthur Bray papers above - Canadian radio engineer, major UFOlogist - directed Canadian government UFO study Project Magnet )
https://biblio.uottawa.ca/atom/index.php/smith-wilbert-b
Marcello Truzzi papers 1970-2003 (Sociologist and UFO/paranormal researcher)
https://caine.emich.edu/archives/findingaids/html/Marcello_Truzzi_papers.html
The Barry H. Downing Manuscript Collection (Presbyterian minister and UFO author/researcher)
E.A. Kral, Paranormal Collection
https://archives.nebraska.edu/repositories/8/resources/699
Robert Alan Goldberg papers 1880-2019 (academic researcher of American fringe social movements)
Carlos Allende papers, 1943-1994 (bulk 1957-1984) (eccentric UFO/aliens researcher and supposed witness to the "Philadelphia Experiment”)
UFO Research Australia – State Library of South Australia (Collection of Australian and overseas UFO organizations; correspondence; reports and analysis of UFO sightings)
https://www.worldcat.org/title/ufo-research-australia/oclc/899304478
Karl Pflock UFO Collection (UFO Researcher and government official)
https://library.osu.edu/collections/SPEC.RARE.CMS.0311/
Harlan J. Smith papers circa 1930-1995 (UT-Austin astronomer)
https://txarchives.org/utcah/finding_aids/03231.xml
Kenn Thomas papers (University of Missouri - St. Louis librarian and conspiracy theory enthusiast)
https://collections.shsmo.org/manuscripts/saint-louis/s1195
https://files.shsmo.org/manuscripts/saint-louis/S1195.pdf (Finding aid)
Open Portal - Online Catalog of InterPsi (paranormal archives at University of Sao Paolo, Brazil. More info, in Portugese http://interpsi.org/portalaberto/)
http://psicologia.ip.usp.br:4000/
Virginia Beach UFO sightings reports, 1946-2009 - Cameron K.F. Pack donation
https://researchworks.oclc.org/archivegrid/collection/data/863431202
Records of the UFO Club of Indiana University of Pennsylvania, 1947-1969
(Formed in the mid-1960s, the UFO Club of IUP was dedicated to researching UFOs. Collection is housed in one archival box, and contains papers about UFO sighting reports, club newsletters, books, magazines, and other related publications.)
Terence McKenna recordings (lectures/interviews, some about UFOs, available on YouTube?)
https://archives.lib.purdue.edu/repositories/2/resources/441
Daniel Rothwell Papers, 1935-2011 (aerospace technical illustrator and UFO researcher)
Dr. Steven Greer (American Ufologist and Disclosure activist) - Document Library and Disclosure Project Intelligence Archive
https://drstevengreer.com/document-library/
National Investigations Committee on Aerial Phenomena (American UFO Research organization)
Philip J. Klass Collection 1948-2000 (American Philosophical Society)
The Curtis Peebles Personal Papers (San Diego Air and Space Museum Library and Archives)
Edward Condon UFO collection, ca. 1947-1969 (American Philosophical Society)
Papers of Donald Howard Menzel (Harvard astronomer and leading UFO skeptic - mostly to Menzel's professional activities and scientific research