Humanists International (known as the International Humanist and Ethical Union, or IHEU, from 1952–2019) is an international non-governmental organisation championing secularism and human rights, motivated by secular humanist values. Founded in Amsterdam in 1952, it is an umbrella organisation made up of more than 160 secular humanist, atheist, agnostic, rationalist, skeptic, freethought and Ethical Culture organisations from over 80 countries.

Humanists International campaigns globally on human rights issues, with a specific emphasis on defending freedom of thought and expression and the rights of the non-religious, who are often a vulnerable minority in many parts of the world. The organisation is based in London but maintains a presence at the United Nations Human Rights Council in Geneva, the United Nations General Assembly in New York, and the Council of Europe in Strasbourg, among other international institutions. Its advocacy work focuses on shaping debates on issues associated with humanism, the rights of the non-religious, and promoting humanist attitudes to social issues.

Humanists International is particularly active in challenging blasphemy and apostasy laws around the world and at the UN. Its annual Freedom of Thought Report indexes the world's countries by treatment of the non-religious and their commitment to freedom of thought and expression. Working with its member organisations, it also helps to coordinate support for those fleeing danger from states which persecute the non-religious. It advocates a humanist approach to various social issues, contributing to bioethical debates and arguing in favour of sexual and reproductive health and rights, LGBT rights, children's rights and women's rights, and in opposition to slavery and caste discrimination.

Outside of its advocacy work, Humanists International functions as the democratic organ of the global humanist movement. It holds a general assembly each year and a World Humanist Congress usually every three years; the last General Assembly was held in Luxembourg in July 2025, and the next Humanist Congress in Ottawa, Canada in August 2026.

Humanists International works to stimulate the growth of humanism and freethought and the spread of Enlightenment values around the world by supporting activists to form effective organisations in their home countries. In 2022, the Humanists International general assembly unanimously adopted the Amsterdam Declaration 2022, which presents as "the official defining statement of World Humanism".

Its official symbol, the Happy Human, is shared with its member organisations worldwide.

In 2022, at the organisation's 70th anniversary General Assembly, delegates voted to replace the previous Amsterdam Declaration 2002 with the Amsterdam Declaration 2022.

Previously, in 2002, at the organisation's 50th anniversary World Humanist Congress, delegates unanimously passed a resolution known as the Amsterdam Declaration 2002, an update of the original Amsterdam Declaration (1952).