Hainfeld is a municipality in the district of Lilienfeld in the Austrian state of Lower Austria.

Following settlements are part of the municipality of Hainfeld (in parentheses population size as of January 1, 2017[3]): Cadastral communities: Gegend Egg, Gölsen, Hainfeld, Heugraben, Kasberg, Landsthal, Ob der Kirche, Saugraben, Vollberg In ancient times the area of Hainfeld was part of the Roman province Noricum.

On 30 December 1888 the Austrian politician Victor Adler united some Austro-Hungarian socialist and worker's movements and associations to the Social Democratic Workers' Party of Austria (German: Sozialdemokratische Arbeiterpartei Österreichs, SDAPÖ) at the party congress in Hainfeld.

On 26 September 1928 the Lower Austrian State Government endowed Hainfeld with town privileges.

After World War II Hainfeld was the second most destroyed Austrian city behind Wiener Neustadt and part of the Soviet occupation zone in Allied-occupied Austria.