Femen (stylized in all caps; Russian and Ukrainian: Фемен, Belarusian: Фэмэн) is a Ukrainian radical feminist activist group whose goal is to protect women's rights. The organization became internationally known for organizing controversial topless protests against sex tourism, religious institutions, sexism, homophobia, and other social, national, and international topics. Founded in Ukraine, the group is now based in France. Femen describes its ideology as being "sextremism, atheism and feminism".

The organization describes itself as "fighting patriarchy in its three manifestations – sexual exploitation of women, dictatorship and religion" and has stated that its goal is "sextremism serving to protect women's rights". Femen activists have been regularly detained by police in response to their protests.

Anna Hutsol is credited as having founded the Femen movement on 10 April 2008, after she became aware of stories of Ukrainian women duped into going abroad and then taken advantage of sexually. However, according to the 2013 documentary by Kitty Green, Ukraine Is Not a Brothel, Femen was founded by Viktor Sviatsky. In September 2013 Inna Shevchenko responded to the documentary stating that Sviatsky "did lead the movement some time ago. ...We accepted this because we did not know how to resist and fight it. ...This is when I decided to leave Ukraine for France to build a new Femen". Femen member Inna Shevchenko discussed Sviatsky with The Independent in January, 2014, and, while not using the word 'founder' said: "I will never deny that he is a smart person. He was the reason why we knew each other. He was one of those smart people around us at the beginning, who were more experienced". Since 2013 Femen has been led by Inna Shevchenko.

Initially, Femen gained attention by demonstrating in skimpy or erotic clothing. For example, on 21 September 2008 in front of the Turkish embassy in Kyiv, a dozen Femen members were dressed as nurses with smudged makeup and high pink heels; however, at the 24 August 2009 demonstration on Ukrainian independence day, Oksana Shachko went topless. Since this approach obtained such great publicity, it rapidly became FEMEN's signature approach. While most of the protests have been confined to bare breasts, in October 2010 Shachko exposed her buttocks outside a locked toilet in a demonstration to protest the lack of public toilets in Kyiv, and four of the group members staged a similar protest in Kyiv in February 2011.

Since May 2011, a host of international news outlets have started to report about the organization's actions; this has sharply heightened Femen's international profile.

From late 2011, the Ukrainian Femen activists started to hold more international protests. In December 2011, three Femen activists stated that the State Security Committee of the Republic of Belarus had abducted and terrorized them after they staged topless protests in Minsk. On 8 April 2013, five Femen members "topless ambushed" Russian President Vladimir Putin (accompanied by German Chancellor Angela Merkel) at the Hanover trade fair.

After Inna Shevchenko chopped down a wooden cross overlooking Maidan Nezalezhnosti in Kyiv on 17 August 2012, she stated that she had received several death threats and that her front door had been kicked in. Fearing arrest, she sought asylum in France and moved to Paris. There, in September 2012, she established a training facility for activists for Femen in France.

In late July 2013, one of the ideologists of the Femen, Viktor Sviatsky, and Hutsol were assaulted on the eve of a visit by Putin to Kyiv to celebrate the 1,025th anniversary of the Christianization of Kievan Rus'. According to Hutsol, those who attacked them "resemble those cooperating with secret services SBU and FSB".