LGBT Humanists UK, founded in 1979, is a special interest section of Humanists UK which campaigns for lesbian, gay, bisexual and transgender (LGBT) equality and human rights in the United Kingdom. It also organises social events for LGBT humanists and public awareness initiatives around Humanism.

It was founded as a separate humanist organisation, the Gay Humanist Group, later the Gay and Lesbian Humanist Association (GALHA). It became a part of the British Humanist Association in 2012, and took on the name Galha LGBT Humanists before becoming LGBT Humanists UK in 2015. The British Humanist Association (BHA) became Humanists UK in 2017.

For many years, its President was the poet Maureen Duffy, who became a Patron of the BHA when the organisations merged. As GALHA, the group was independently affiliated with the International Humanist and Ethical Union (IHEU) and the NGO Amnesty International. The group is led by volunteers. Past chairs include Andrew Copson, the chief executive of the BHA, who is also President of IHEU.

The Gay Humanist Group was originally founded in response to the Gay News 'blasphemy' trial by members of the Campaign for Homosexual Equality at their Brighton conference in August 1979. The group had been responded in response to unfounded accusations by Mary Whitehouse that a "gay humanist lobby" was influencing public opinion and public policy. The founding members of the Gay Humanist Group thought that, while Whitehouse's claims were unfounded and untrue, that a gay humanist lobby group was a good idea and indeed one urgently needed. The Gay Humanist Group became GALHA (Gay and Lesbian Humanist Association) in 1987. It later became Galha LGBT Humanists in 2012, and then LGBT Humanists in 2015.

In 1983, LGBT Humanists lobbied Amnesty International to begin providing support for gays and lesbians in countries where people were persecuted for their sexuality. That same year, it innovated a 'Postal Action Group' that enabled its own members to lobby their MPs, ministers, and companies on 'gay and humanist rights' issues, akin to 21st century mass email lobbying tools. In 1989, Anthony Grey from the Homosexual Law Reform Society congratulated LGBT Humanists on its 10th anniversary, saying "Constantly having to combat irrational and dangerous thinking is strenuous and sometimes tedious, but not necessarily boring. It can be fun. And as no-one else is doing it as consistently and effectively as is necessary. I hope that GHG will concentrate on a demolition job of much of the silly rubbish that is still spouted about homosexuality."

Having been founded in response to a blasphemy trial, free speech also remained a perennial focus for the group, which extended "unequivocal" support to Humanists UK patron Salman Rushdie during the Rushdie affair in which he received a death sentence from Islamic fundamentalists in 1989. LGBT Humanists was at the forefront of the humanist movement's campaign against Section 28 (which prevented public authorities from acknowledging the existence of homosexuality, with numerous side effects such as schools not tackling homophobic bullying).

From its inception, the Gay Humanist Group worked to combat widespread prejudice and religious bigotry towards LGBT people in the UK, at a time when attitudes to homosexuality were still fairly negative on the whole. Since that time the organisation has played key roles in UK-wide campaigns for LGBT equality, particularly marriage rights for LGBT couples. The group had provided non-recognised humanist marriage ceremonies for same-sex couples since the 1980s, and coordinated a number of such ceremonies outside Parliament to inspire legislative action.

Two significant milestones came in 1987, when in partnership with Channel 4, the group organised a "live gay wedding" on terrestrial television, which in turn was the first same-sex kiss between men ever shown on British television, and later when the Hippodrome nightclub in London hosted a high-profile event where the group conducted 22 simultaneous gay weddings. Another came in 1999 when 11 couples, including the activist Barbara Smoker, were married on-screen for the BBC Two show Gaytime TV. A 2000 "kiss-in" protest outside Parliament later precipitated Mayor of London Ken Livingstone's London Partnership Register in 2001, which in turn provided inspiration for the 2005 Civil Partnership Act and the Marriage (Same Sex Couples) Act in 2013. LGBT Humanists was also part of the Equal Love Campaign which in 2011 attempted to bring a case to the European Court of Human Rights concerning same-sex civil marriages and opposite-sex civil partnerships.