The pulmonary artery catheter (PAC), used first in the 1970s, remains an essential tool in advanced hemodynamic monitoring despite the presence of less invasive alternatives. This chapter provides an extensive review of the PAC’s principles, clinical applications, and its role in critical care. It includes detailed anatomy and insertion technique of the PAC, focusing on its capability to provide real-time measurements of key parameters such as pulmonary artery pressure, pulmonary capillary wedge pressure, cardiac output, and mixed venous oxygen saturation. These measurements enable the accurate evaluation of volume status, cardiac function, and oxygen delivery, particularly in managing complex conditions such as shock, heart failure, and perioperative instability. The clinical utility of PAC in intensive care units and major surgeries is reinforced, along with its superiority in situations requiring detailed hemodynamic assessment. Despite risks associated with its use, including insertion-related complications and data misinterpretation, technological advancements and integration with personalized medicine continue to support its relevance. The PAC remains a gold standard for managing critically ill patients where high-precision, real-time cardiovascular parameters are essential for optimizing outcomes.