Sam Smith: Singer wants to be called 'they' instead of 'he'
In a post to their 13.4 million followers on Instagram, the chart-topping singer-songwriter said they had come to the decision after spending "a lifetime of being at war" with their gender.
Smith, 27, revealed earlier this year that they had questioned their gender and had at one time considered a sex change.
A person who identifies as non-binary does not define themselves exclusively as masculine or feminine? and generally prefers they/them pronouns, rather than he/she.
Smith said: "Today is a good day so here goes. I've decided I am changing my pronouns to THEY/THEM after a lifetime of being at war with my gender I've decided to embrace myself for who I am, inside and out.
"I'm so excited and privileged to be surrounded by people that support me in this decision but I've been very nervous about announcing this because I care too much about what people think but f*** it!
"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.
"P.s. 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.
"If you have questions and are wondering what this all means I'll try my best to explain but I have also tagged below the human beings who are fighting the good fight everyday.
"These are activists and leaders of the non binary/trans community that have helped me and given me so much clarity and understanding."
In an interview with actress and body positivity activist Jameela Jamil on her I Weigh show in March, Smith said that they did not identify as male or female.
And last month Smith shared a message on Instagram in which they told fans that they had gone through 18 months of "challenging" therapy, but that they were now in a more positive place.
Smith also recently began wearing clothes traditionally considered to be female in public.
At the GQ Men of the Year Awards in London last week, Smith walked the red carpet wearing high heels, posting before the show: "I'd never ever ever be able to be myself like this in front of the industry or anyone."
Mark Ronson and Jamil were among a clutch of stars who left messages of encouragement under Smith's post.
Jamil said: "I love you. I'm proud to call you my friend."
Chart-topping producer Ronson added: "Can I get them on a track pls."
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."