Health care (or healthcare) is the diagnosis, treatment, and prevention of disease, illness, injury, and other physical and mental impairments in humans. Health care is delivered by practitioners in medicine, chiropractic, dentistry, nursing, pharmacy, allied health, and other care providers. It refers to the work done in providing primary care, secondary care and tertiary care, as well as in public health.

Access to health care varies across countries, groups and individuals, largely influenced by social and economic conditions as well as the health policies in place. Countries and jurisdictions have different policies and plans in relation to the personal and population-based health care goals within their societies. Health care systems are organizations established to meet the health needs of target populations. Their exact configuration varies from country to country. In some countries and jurisdictions, health care planning is distributed among market participants, whereas in others planning is made more centrally among governments or other coordinating bodies. In all cases, according to the World Health Organization (WHO), a well-functioning health care system requires a robust financing mechanism; a well-trained and adequately-paid workforce; reliable information on which to base decisions and policies; and well maintained facilities and logistics to deliver quality medicines and technologies.

Health care can form a significant part of a country's economy. In 2008, the health care industry consumed an average of 9.0 percent of the gross domestic product (GDP) across the most developed OECD countries. The United States (16.0%), France (11.2%), and Switzerland (10.7%) were the top three spenders.

Health care is conventionally regarded as an important determinant in promoting the general health and wellbeing of peoples around the world. An example of this is the worldwide eradication of smallpox in 1980—declared by the WHO as the first disease in human history to be completely eliminated by deliberate health care interventions.