Arterial hypertension is a significant cardiovascular risk factor, the diagnosis and treatment of which is of immense health and socioeconomic relevance worldwide. Arterial hypertension is defined as a systolic value ≥140 mmHg and/or a diastolic value ≥90 mmHg. In addition to office blood pressure measurement, the diagnosis should be verified using office-independent measurements. Pathophysiologically, an increased activity of the renin-angiotensin-aldosterone system with consequently increased sympathetic tone is often the cause of the development of arterial hypertension. This forms the basis of essential medicinal and interventional treatment approaches. A multitude of clinical studies have so far been able to substantiate their positive prognostic effect. The following book chapter provides—based on current guideline recommendations—an overview of the definition of arterial hypertension, its diagnosis and therapy. More than 1.2 billion people worldwide suffer from arterial hypertension (Forouzanfar et al., JAMA 317(2):165–182, 2017), where in many cases, it is neither adequately diagnosed nor sufficiently treated (Zhou et al., Lancet 394(10199):639–651, 2019). Arterial hypertension is one of the most important risk factors for cardiovascular morbidity and mortality and is responsible for a multitude of sequelae (Forouzanfar et al., Lancet 388(10053):1659–1724, 2016). Arterial hypertension is therefore one of the most common cardiovascular diseases with enormous socioeconomic consequences.