This corpus of letters contains previously unpublished letters from Carl Hauptmanns first wife Martha Hauptmann, née Thienemann (1862-1939), which she wrote to her husband. During the research for this edition, the holdings in the Carl Hauptmann Archive of the University of Wroclaw/Bresla, in the Archiv der Akademie der Künste in Berlin, in the Gerhart-Hauptmann-Museum Erkner and in the Carl Hauptmann-Nitsche collection in the Deutsche Literaturarchiv Marbach/N. as well as in the Carl and Gerhart Hauptmann House in Szklarska Poreba/Schreiberhau were assessed. The letters are an important source of information about Carl Hauptmanns life and work: among other things, they offer intimate insights into Hauptmanns development from scientist to poet, his family life and also his literary activity, for which Martha Hauptmann showed great interest even after their divorce. The letters were accurately transcribed and annotated by Agnieszka Godlewska and the appendix provides (auto)biographical information about Martha Hauptmann.