This Festschrift volume, published in memory of Harald Ganzinger, contains 17 papers from colleagues all over the world and covers all the fields to which Harald Ganzinger dedicated his work during his academic career. The volume begins with a complete account of Harald Ganzinger’s work and then turns its focus to the research of his former colleagues, students, and friends who pay tribute to him through their writing. Their individual papers span a broad range of topics, including programming language semantics, analysis and verification, first-order and higher-order theorem proving, unification theory, non-classical logics, reasoning modulo theories, and applications of automated reasoning in biology.