Supraventricular tachycardias (SVTs) are fast heart rhythms that originate above the ventricles. This chapter discusses many types of these arrhythmias including premature atrial complexes (PACs), atrial fibrillation, atrial flutter, atrial tachycardia, and paroxysmal supraventricular tachycardia. Atrial fibrillation and flutter are common, chaotic arrhythmias that increase the risk of stroke and may require anticoagulation or catheter ablation. Abnormal connections can arise within the atrioventricular node that can disrupt normal conduction and result in a fast arrhythmia known as paroxysmal supraventricular tachycardia. Connections between the atria and ventricles, known as accessory pathways, can also occur and include conditions like Wolff-Parkinson-White syndrome that involve abnormal circuits that can also lead to syncope and cardiac arrest. Many of these arrhythmias can be managed using medications, with catheter ablation offering a curative option.