Angiotensin II is a hormone that plays a crucial role in regulating blood pressure and fluid balance in the body. It is produced from a precursor called angiotensin I through the action of an enzyme known as angiotensin-converting enzyme (ACE). Angiotensin II causes blood vessels to constrict, which increases blood pressure, and stimulates the release of aldosterone, a hormone that promotes sodium and water retention. In addition to its effects on blood pressure, angiotensin II also influences the nervous system and can affect the release of other hormones. It is involved in various physiological processes, including the regulation of thirst and the control of electrolyte balance. Due to its significant role, angiotensin II is a target for certain medications used to treat high blood pressure and heart failure.