A sphygmomanometer (/ˌsfɪɡmoʊməˈnɒmɪtər/ SFIG-moh-mə-NO-mi-tər), also known as a blood pressure monitor, blood pressure machine, or blood pressure gauge, is a device used to measure blood pressure, composed of an inflatable cuff to collapse and then release the artery under the cuff in a controlled manner, and a mercury or aneroid manometer to measure the pressure. Manual sphygmomanometers are used with a stethoscope when using the auscultatory technique.

A sphygmomanometer consists of an inflatable cuff, a measuring unit (the mercury manometer, or aneroid gauge), and a mechanism for inflation which may be a manually operated bulb and valve or a pump operated electrically.

The word sphygmomanometer uses the combining form of sphygmo- + manometer. The roots involved are as follows: Greek σφυγμός sphygmos "pulse", plus the scientific term manometer (from French manomètre), i.e. "pressure meter", itself coined from μανός manos "thin, sparse", and μέτρον metron "measure".

Most sphygmomanometers were mechanical gauges with dial faces, or mercury columns, during most of the 20th century. Since the advent of electronic medical devices, names such as "meter" and "monitor" can also apply, as devices can automatically monitor blood pressure on an ongoing basis.

The sphygmomanometer was invented by Samuel Siegfried Karl Ritter von Basch in the year 1881. Scipione Riva-Rocci introduced a more easily-usable version in 1896. In 1901, pioneering neurosurgeon Dr. Harvey Cushing brought an example of Riva-Rocci's device to the US, modernized and popularized it within the medical community. Further improvement came in 1905 when Russian physician Nikolai Korotkov included diastolic blood pressure measurement following his discovery of "Korotkoff sounds". William A. Baum invented the Baumanometer brand in 1916, while working for The Life Extension Institute which performed insurance and employment physicals.

Both manual and digital meters are currently employed, with different trade-offs in accuracy versus convenience.

A stethoscope is required for auscultation (see below). Manual meters are best used by trained practitioners, and, while it is possible to obtain a basic reading through palpation alone, this yields only the systolic pressure.

Digital meters employ oscillometric measurements and electronic calculations rather than auscultation. They may use manual or automatic inflation, but both types are electronic, easy to operate without training, and can be used in noisy environments. They calculate systolic and diastolic pressures by oscillometric detection, employing either deformable membranes that are measured using differential capacitance, or differential piezoresistance, and they include a microprocessor. They estimate mean arterial blood pressure and measure pulse rate; while systolic and diastolic pressures are obtained less accurately than with manual meters, and calibration is also a concern. Digital oscillometric monitors may not be advisable for some patients, such as those with arteriosclerosis, arrhythmia, preeclampsia, pulsus alternans, and pulsus paradoxus, as their calculations may not be correct for these conditions, and in these cases, an analog sphygmomanometer is preferable when used by a trained person.