A hospital is a healthcare institution providing patient treatment with specialized health science and auxiliary healthcare staff and medical equipment. The best-known type of hospital is the general hospital, which typically has an emergency department to treat urgent health problems ranging from fire and accident victims to a sudden illness. A district hospital typically is the major health care facility in its region, with many beds for intensive care and additional beds for patients who need long-term care.

Specialized hospitals include trauma centers, rehabilitation hospitals, children's hospitals, geriatric hospitals, and hospitals for specific medical needs, such as psychiatric hospitals for psychiatric treatment and other disease-specific categories. Specialized hospitals can help reduce health care costs compared to general hospitals. Hospitals are classified as general, specialty, or government depending on the sources of income received.

A teaching hospital campus combines patient care with teaching to health science students, auxiliary healthcare students, and qualified medical graduates completing their postgraduate residencies before licensure to practice. A health science facility smaller than a hospital is generally called a clinic. Hospitals have a range of departments (e.g. surgery and urgent care) and specialist units such as cardiology. Some hospitals have outpatient departments and some have chronic treatment units. Common support units include a pharmacy, pathology, and radiology. Facilities that combine many health care functions, including general or specialized patient care, teaching, research, and so on, may use the term medical center. This term can also refer to an office complex with various unaffiliated health services or any kind of clinic or hospital.

A large hospital or medical center also often serves as the administrative headquarters of a larger health system which may have multiple sites.

Hospitals are typically funded by public funding, health organizations (for-profit or nonprofit), health insurance companies, or charities, including direct charitable donations. Historically, hospitals were often founded and funded by religious orders, or by charitable individuals and leaders.

Hospitals are currently staffed by professional physicians, surgeons, nurses, and allied health practitioners. In the past, however, this work was usually performed by the members of founding religious orders or by volunteers. However, there are various Catholic religious orders, such as the Alexians and the Bon Secours Sisters that still focus on hospital ministry in the late 1990s, as well as several other Christian denominations, including the Methodists and Lutherans, which run hospitals. In accordance with the original meaning of the word, hospitals were original "places of hospitality", and this meaning is still preserved in the names of some institutions such as the Royal Hospital Chelsea, established in 1681 as a retirement and nursing home for veteran soldiers.

During the Middle Ages, hospitals served different functions from modern institutions in that they were almshouses for the poor, hostels for pilgrims, or hospital schools. The word "hospital" comes from the Latin hospes, signifying a stranger or foreigner, hence a guest. Another noun derived from this, hospitium came to signify hospitality, that is the relation between guest and shelterer, hospitality, friendliness, and hospitable reception. By metonymy, the Latin word then came to mean a guest-chamber, guest's lodging, an inn. Hospes is thus the root for the English words host (where the p was dropped for convenience of pronunciation) hospitality, hospice, hostel, and hotel. The latter modern word derives from Latin via the Old French romance word hostel, which developed a silent s, which letter was eventually removed from the word, the loss of which is signified by a circumflex in the modern French word hôtel. The German word Spital shares similar roots.

Some patients go to a hospital just for diagnosis, treatment, or therapy and then leave ("outpatients") without staying overnight; while others are "admitted" and stay overnight or for several days or weeks or months ("inpatients"). Hospitals are usually distinguished from other types of medical facilities by their ability to admit and care for inpatients whilst the others, which are smaller, are often described as clinics.