Sam Smith has asked fans to use the pronouns "they/them", not "he/him", after coming out as non-binary.
The pop star wrote on Instagram: "After a lifetime of being at war with my gender I've decided to embrace myself for who I am, inside and out."
The singer added: "I've been very nervous about announcing this because I care too much about what people think."
Six months ago, Smith said they did not feel male or female, but "I flow somewhere in between".
On Friday, the 27-year-old said they had been "surrounded by people that support me in this decision".
They wrote: "I understand there will be many mistakes and mis-gendering but all I ask is you please please try. I hope you can see me like I see myself now. Thank you."
The singer went on to say: "I am at no stage just yet to eloquently speak at length about what it means to be non binary but I can't wait for the day that I am. So for now I just want to be VISIBLE and open."
At last week's GQ Men of the Year Awards, Smith walked the red carpet wearing high heels, posting: "I'd never ever ever be able to be myself like this in front of the industry or anyone."
By Ben Hunte, LGBT correspondent
Adopting pronouns of they/them may be a new concept to many people, but those familiar with the LGBT community will be aware that this often accompanies non-binary identities.
For a long time, several of those who identify as non-binary have called for wider awareness of the issues they face being themselves on a daily basis.
With no specifically non-binary charities in the UK, some people in the community say they are suffering in silence.
From street harassment for not matching up to their assigned gender and the associated stereotypes, to those in the hospitality industry referring to them as "sir" or "madam", it can be challenging.
Using they/them pronouns can help non-binary individuals to feel more accepted.
Today, some LGBT people are saying that this spotlight on non-binary lives is exactly what the community has needed.
Toryn Glavin, trans engagement manager at LGBT charity Stonewall, said: "We're delighted that Sam Smith feels able to speak openly about their gender identity, and their visibility will have a huge impact on many non-binary people.
"Sadly we know that it is still far too hard for people to be open and accepted for who they are, and we will keep campaigning until every LGBT person is accepted without exception."
What does Sam Smith's announcement mean to the LGBT community?
Speaking at London's first ever Trans Pride event, Aisha Brown, 37, welcomed Smith's announcement, saying: "We definitely need more non-binary people in the public space, being visibly non-binary.
"People have incredibly diverse experiences of being non-binary and transgender, but it's a very wide community and we welcome everyone."
Jake Gallagher, 27, says it is "great" Smith has come out as non-binary, adding: "The more people in the mainstream that come out as trans or non-binary is just going to help, especially someone like Sam, who has got a large platform.
"For him to spread the message is very important, it will get to a lot of people in small towns and villages outside of London."