The sinoatrial node (SAN) is a specialised group of pacemaker cells located in the right atrium that generates electrical impulses to initiate and regulate the heart’s rhythmic contractions. It is critical in clinical practice as the primary driver of normal sinus rhythm, and dysfunction can lead to arrhythmias such as sick sinus syndrome, which may require intervention like pacemaker implantation. Understanding SAN function is essential for diagnosing and managing heart rate abnormalities and their impact on cardiac output.