Hans-Joachim Klein (; born 1947) is a former member of the German left-wing militant group Revolutionary Cells (RZ). His "nom de guerre" was "Angie". In 1975, Klein participated in an attack on OPEC headquarters in Vienna organized by the international terrorist "Carlos the Jackal", in which he was seriously injured. He publicly renounced political violence two years later. After decades in hiding, he was arrested in 1998, prosecuted for his role in the OPEC attack, and sentenced to nine years' imprisonment. He was paroled in 2003.