Acute heart failure (HF) is the most common diagnosis at discharge in patients aged >65years. It carries a dismal prognosis with a high in-hospital mortality and very high post-discharge mortality and re-hospitalization rates. It is a complex clinical syndrome that cannot be described as a single entity as it varies widely with respect to underlying pathophysiologic mechanisms, clinical presentations and, likely, treatments. It is the aim of this paper to describe some of the main clinical presentations of acute HF. Amongst them, we will consider de novo HF versus acutely decompensated chronic HF, HF caused, and/or worsened, by myocardial ischemia, acute HF with low, normal, or high systolic blood pressure, acute HF caused by lung congestion or fluid retention or fluid redistribution to the lungs, and acute HF with comorbidities (diabetes, anemia, renal insufficiency, etc.). Different pathophysiologic mechanisms and clinical presentations may coexist in the same patient. Identification and, whenever possible, treatment of underlying pathophysiologic mechanisms may become important for acute HF management.