A humanist celebrant or humanist officiant is a person who performs humanist celebrancy services, such as non-religious weddings, funerals, child namings, coming of age ceremonies and other rituals. Some humanist celebrants are accredited by humanist organisations, such as Humanists UK, Humanist Society Scotland (HSS), The Humanist Society (US), and the Humanist Association of Canada (HAC).

Humanist ceremonies are conducted in every part of the world by humanist organizations, although the legal status of non-religious ceremonies of different kinds varies from place to place. In general, funeral ceremonies are not typically regulated by states, but many countries with a religious history have stricter guidelines on who can perform legal marriages. Naming ceremonies, similarly, can be held anywhere without legal implications. In countries where legal marriages can only be performed by religious institutions or the state (such as England), humanist weddings are often performed before or after a civil legal proceeding, but presented as the more meaningful or significant of the two events.

As of 2021, humanist celebrants can conduct legally binding marriage ceremonies in Scotland, Ireland, Northern Ireland, Jersey, Guernsey, Norway, Iceland, Australia, New Zealand, South Africa, Canada and the United States.

The charity Humanists UK (formerly the British Humanist Association) pioneered the practice of offering humanist ceremonies, and today organises a network of celebrants or officiants across England, Wales and Northern Ireland. A similar network exists in Scotland, where, following a June 2005 ruling by the Registrar General, celebrants belonging to approved humanist associations have been permitted to conduct legal wedding ceremonies. Humanists UK celebrants in Northern Ireland were given the same rights in 2017 following a court case supported by Humanists UK.

In England and Wales the current legal position is that a humanist wedding or partnership ceremony must be supplemented by obtaining a civil marriage or partnership certificate through a Register Office. In December 2014 it was reported that the Prime Minister's Office was blocking the implementation of a change to give legal force to humanist weddings in England and Wales. That same year in Scotland, when same-sex marriage was legalised, the First Minister of Scotland attended the legal humanist marriage of a same-sex couple. In 2015, humanist weddings became more popular in Scotland than Church of Scotland weddings, or those of any religious denomination. The Humanist Society Scotland's status as a provider of humanist marriages in Scotland was reflected in statute from 2017 onwards.

Non-religious funerals are legal within the UK. Humanist celebrants are familiar with the procedures of cremation and burial, and are trained and experienced in devising and conducting suitable ceremonies. The British Humanist Association has in the past described officiants as follows:

Officiants are generally at least 35 years old, have experience of public speaking, and have probably had paid or voluntary experience in a caring/supporting profession – such as nursing, teaching, police or social work, for example. They must be able to cope with the emotional burden of regularly meeting and working with bereaved people - often in relation to particularly difficult or unexpected deaths, such as the death of a child in a road accident. Funeral directors are able to make arrangements with trained officiants in their local area.

Humanist funerals have reportedly been held in recent years for Claire Rayner, Keith Floyd, Linda Smith, Ronnie Barker, Lynsey de Paul, Terry Jones, Victoria Wood, Doris Lessing, John Noakes, David Nobbs, Cynthia Payne, Dale Winton, and Bob Monkhouse, among others. The humanist funeral for former First Minister of Wales Rhodri Morgan in 2017 was the first national funeral in the United Kingdom to be led by a humanist celebrant, former AM Lorraine Barrett, as well as the first national funeral held in Wales.