| May 01 | International Labour Day or International Worker’s Day or May Day. | |
| May 01 (First Sunday in May) | World Laughter Day | |
| May 02 | World Tuna Day | Our Tuna, Our Heritage |
| May 03 | World Press Freedom Day | Journalism under digital siege |
| May 04 | International Firefighters’ Day | |
| May 03 (First Tuesday of May) | World Asthma Day | Closing Gaps in Asthma Care |
| May 05 | International Day of the Midwife (IMDB) | 100 Years of Progress |
| May 05 | World Hand Hygiene Day | Health care quality and safety climate or culture |
| May 06 | International No Diet Day | |
| May 08 | World Red Cross and Red Crescent Day | #BeHumanKind |
| May 08 | World Thalassemia Day | Be Aware. Share. Care: Working with the global community as one to improve thalassemia knowledge |
| May 14 (Second Saturday of May) | World Migratory Bird Day | Light Pollution |
| May 08 and 09 | Time of Remembrance and Reconciliation for Those Who Lost Their Lives during the Second World War | |
| May 10 | International Day of Argania | The Argan tree, symbol of resilience |
| May 12 | International Nurses Day | Nurses: A Voice to Lead – Invest in Nursing and respect rights to secure global health |
| May 15 | International Spring Astronomy Day | |
| May 15 | International Day of Families | Families and Urbanization |
| May 16 | International Day of Living Together in Peace | United in differences and diversity |
| May 16 | International Day of Light (IDL) | Basic Sciences for Sustainable Development and Glass |
| May 17 | World Telecommunication and Information Society Day (WTISD) | Digital Technologies For Older Persons And Healthy Ageing |
| May 17 | World Hypertension Day (WHD) | Measure Your Blood Pressure Accurately, Control It, Live Longer |
| May 18 | International Museum Day | The Power of Museums |
| May 18 | World AIDS Vaccine Day | |
| May 20 | World Bee Day | Bee Engaged: Celebrating the diversity of bees and beekeeping systems |
| May 20 | World Metrology Day | Metrology in the Digital Era |
| May 21 | International Tea Day | Tea and Fair Trade |
| May 21 | World Day for Cultural Diversity for Dialogue and Development | |
| May 20 (Third Friday in May) | Endangered Species Day | Recovering key species for ecosystem restoration |
| May 22 | International Day for Biological Diversity (World Biodiversity Day) | Building a shared future for all life |
| May 23 | International Day to End Obstetric Fistula | End Fistula Now: Invest in Quality Healthcare, Empower Communities! |
| May 23 | World Turtle Day | Shellebrate |
| May 25 | International Missing Children’s Day (IMCD) | |
| May 25 | World Thyroid Day | Thyroid and Communication |
| May 25 to 31 | International Week of Solidarity with the Peoples of Non-Self-Governing Territories | |
| May 28 | World Hunger Day | #YouthEndingHunger |
| May 28 | International Day of Action for Women’s Health (International Women’s Health Day) | Resist and Persist |
| May 28 | Amnesty International Day | |
| May 29 | World Digestive Health Day (WDHD) | Colorectal Cancer Prevention: Getting Back on Track |
| May 29 | International Everest Day | |
| May 29 | International Day of United Nations Peacekeepers | People Peace Progress: The Power of Partnerships |
| May 31 | World No Tobacco Day (WNTD) | Tobacco: Threat to our environment |
