Ad Adstra was a science fiction fanzine published in the United States by Mark Reinsberg. It ran five issues from May 1939 to November 1940. Two pages of the unfinished sixth issue appeared later in the fanzine Midwest Marky.
Henry Bott, Leslie A. Crouth, W. Lawrence Hamling, Erle Korshak, Julian S. Krupa, and Richard I. Meyer were also listed on the masthead for various issues.
Contributors included Forrest J Ackerman, John W. Campbell Jr., Leslie A. Croutch, Hugo Gernsback, Jack Darrow, Jack Erman, Larry B. Farsaci, Joseph Gilbert, J. Harvey Haggard, W. Lawrence Hamling, Charles D. Hornig, Erle Korshak, Henry Kuttner, Robert W. Lowndes, Robert A. Madle, Gerald W. Meader, Richard I. Meyer, Raymond A. Palmer, Clifford D. Simak, E.E. "Doc" Smith, Harry Warner Jr., Art Widner, Jack Williamson, and Donald A. Wollheim.
Julian S. Krupa was the art editor, and provided the cover art for four of the five issues, and some interior artwork.