<p>Over the past five decades, prone positioning has evolved from single case reports to an evidence-based intervention. Initially used as a rescue therapy, it is now recognized as an integral component of lung-protective mechanical ventilation strategies, applied early in intubated patients with acute respiratory distress syndrome (ARDS) with a PaO₂/F_IO₂ ratio &lt; 150&#xa0;mmHg. The COVID-19 pandemic further expanded its use to non-intubated patients, the so-called awake prone position (APP), with promising results. APP requires confirmation in non-COVID patients and in a more routine ICU practice. Improved oxygenation is a consistent and well-recognized effect of prone positioning in both intubated and non-intubated patients with ARDS. Beyond its effects on gas exchange, prone positioning mitigates ventilator-induced lung injury by reducing lung stress and strain and may also confer favorable hemodynamic effects. This article reviews the physiologic rationale for prone positioning, evidence from randomized controlled trials, current guideline recommendations, practical aspects of implementation, and ongoing questions in both intubated and non-intubated patients.</p> Visual abstract <p></p>