International Nurses Day (IND) is an international day celebrated around the world on 12 May (the anniversary of Florence Nightingale's birth) of each year, to mark the contributions nurses make to society.

World Red Cross and Red Crescent Day is an annual celebration of the principles of the International Red Cross and Red Crescent Movement. World Red Cross Red Crescent Day is celebrated on 8 May each year. This date is the anniversary of the birth of Henry Dunant (born 8 May 1828), the founder of International Committee of the Red Cross (ICRC) and the recipient of the first Nobel Peace Prize.

World Day for Cultural Diversity for Dialogue and Development, Anti-Terrorism Day of India celebrated on May 21.

International Museum Day (IMD) is an international day a celebration that held every year on or around 18 May, coordinated by the International Council of Museums (ICOM). The event highlights a specific theme that changes every year and that is at the heart of the international museum community’s preoccupations.

International Workers' Day, also known as Labour Day in some countries, and often referred to as May Day, is a celebration of labourers and the working classes that is promoted by the international labour movement which occurs every year on May Day (1 May), an ancient European spring festival.

World No Tobacco Day (WNTD) is observed around the world every year on May 31. It is intended to encourage a 24-hour period of abstinence from all forms of tobacco consumption around the globe. The day is further intended to draw attention to the widespread prevalence of tobacco use and to negative health effects, which currently lead to nearly 6 million deaths each year worldwide, including 600,000 of which are the result of non-smokers being exposed to second-hand smoke. The member states of the World Health Organization (WHO) created World No Tobacco Day in 1987. In the past twenty-nine years, the day has been met with both enthusiasm and resistance around the globe from governments, public health organizations, smokers, growers, and the tobacco industry.

The International Day of Families is observed on the 15th of May every year. The Day was proclaimed by the UN General Assembly in 1993 with resolution A/RES/47/237 and reflects the importance the international community attaches to families. The International Day provides an opportunity to promote awareness of issues relating to families and to increase knowledge of the social, economic and demographic processes affecting families.

World Thyroid Day celebrated on May 25.

28th May celebrated as International Day of Action for Women’s Health.

World Hypertension Day(WHD) is a day designated and initiated by The World Hypertension League (WHL), which is itself an umbrella to organizations of 85 national hypertension societies and leagues. The day was initiated to increase the awareness of hypertension. This was especially important because of the lack of appropriate knowledge among hypertensive patients. The WHL launched its first WHD on May 14, 2005. Since 2006, the WHL has been dedicating May 17 of every year as WHD.