Heinrich Mertens (6 February 1906 – 16 June 1968) was a German publicist, editor of the magazine The Red Book of Catholic Socialists, and mayor of Halle and Jena.
These were young Catholics who did social work free of charge while renouncing official titles and organizational structure and leading a consciously modest life.
In Vienna he also joined a group affiliated with Catholic social reformer Anton Orel (1881–1959) publisher of the weekly "Das neue Volk" (The New People).
Mertens however came to regard Orel's social-romantic anticapitalism as out-of-date and unsuitable for everyday living and, while preferring socialism to capitalism, nevertheless rejected the materialistic and atheistic elements of Marxist doctrine.
He then joined the editorial board of the Social Democratic "Rheinische Zeitung" on the recommendation of Wilhelm Sollmann (1881-1951) and became the editor of the supplement "The Tribune", an ongoing dialogue between Christians and socialists.
As a scholar supported by the Abraham Lincoln Stiftung (endowed by the Rockefeller Foundation), Mertens studied philosophy, economics, pedagogy and psychology during the summer semester of 1932 in Frankfurt.
In February 1936, Mertens was arrested by the Gestapo as part of the trial of the Catholic priest Joseph Rossaint (1902–1991) on the charge of high treason.
With the end of the war, Heinrich Mertens was appointed mayor of Eisleben by the US armed forces on April 14, 1945, a position which he held until 31 October.