National Technology Day of India celebrated on May 11.

The "International Day of United Nations Peacekeepers", May 29, is "a day to pay tribute to all the men and women who have served and continue to serve in United Nations peacekeeping operations for their high level of professionalism, dedication, and courage and to honor the memory of those who have lost their lives in the cause of peace."

The United Nations General Assembly declared May 3 to be World Press Freedom Day or just World Press Day to raise awareness of the importance of freedom of the press and remind governments of their duty to respect and uphold the right to freedom of expression enshrined under Article 19 of the 1948 Universal Declaration of Human Rights and marking the anniversary of the Windhoek Declaration, a statement of free press principles put together by African newspaper journalists in Windhoek in 1991.

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

The International Day for Biological Diversity (or World Biodiversity Day) is a United Nations–sanctioned international day for the promotion of biodiversity issues. It is currently held on May 22.

1st Tuesday of May celebrated as World Asthma Day.

World Chronic Fatigue Syndrome Awareness Day celebrated on May 12.

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 Telecommunication and Information Society Day and ,Information Society Day celebrated on May 17.

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