HIAG (German: Hilfsgemeinschaft auf Gegenseitigkeit der Angehörigen der ehemaligen Waffen-SS, lit. 'Mutual aid association of former Waffen-SS members') was a lobby group and a denialist veterans' organisation founded by former high-ranking Waffen-SS personnel in West Germany in 1951. Its main objective was to achieve legal, economic, and historical rehabilitation of the Waffen-SS.

To achieve these aims, the organisation used contacts with political parties, and employed multi-prong historical negationism and propaganda efforts, including periodicals, books, and public speeches. A HIAG-owned publishing house, Munin Verlag, served as a platform for its publicity. This extensive body of work, 57 book titles and more than 50 years of monthly periodicals, has been described by historians as revisionist apologia.

Always in touch with its members' Nazi past, HIAG was a subject of significant controversy, both in West Germany and abroad. The organisation drifted into open far-right extremism in its later history; it disbanded in 1992 at the federal level, but local groups continue to exist into the 21st century. Its monthly periodical, Der Freiwillige, survived until 2014. While HIAG only partially achieved its goals of legal and economic rehabilitation of the Waffen-SS, its propaganda efforts led to the reshaping of the image of the Waffen-SS in popular culture.