"Coming out" as gay still feels harder in Britain than standing for election or being interviewed on live television, Scottish Secretary David Mundell said as he revealed his sexuality.
Mr Mundell, who becomes the first openly-gay Tory cabinet minister, said resolving to go public this year was "one of the most important decisions of my life".
In a statement he said he could not "fully rationalise" why it was such a struggle for him - and many others - but had come to understand "the only way to be truly happy on a personal level is to acknowledge in public as well as in private, who I am".
"I so admire the many people, young and old, who are doing this every day, uncertain of the reaction. I have been very fortunate and couldn't have had more love and support from my family and friends," he wrote on his website.
"However, making this public is something I have had to do myself. I don't know what the wider reaction will be, but I know it's the right thing for me to do.
"Other than the intensely personal and positive difference it makes to me, and the way I can live my life, my hope is that my coming out doesn't change anything else about how I go about my work or how people treat me.
"Gender and sexuality should make no difference whether you are a cabinet minister or in any other walk of life and I hope that I can, in my own way, reinforce that message."
The leader of the Scottish Conservative Party, Ruth Davidson - who is also gay - said her colleague had her "wholehearted support, as well as the support of the wider Scottish Conservative family".
"I know that David didn't make today's statement lightly, but approached it in his typically thoughtful and positive manner," she wrote on Twitter.
Mr Mundell's announcement brings the number of openly-gay MPs to 33 - the highest proportion of any Parliament in the world, according to a study by US academics - and means there are as many on the Tory as the Labour benches (13).
Labour's Wes Streeting said: "Still not as easy as it should be, but a lot easier than it once was."
A senior Downing Street source said David Cameron had been informed in the past few days of Mr Mundell's decision to issue a statement.
Asked if the Prime Minister offered his warm support to the Scotland Secretary, the source said: "Of course, absolutely."
He added: "I'm not going to get into their private conversation, and it's obviously a very personal statement, but the PM is very pleased and delighted that he is in a position to take this step, and it's very encouraging to see."
Challenged over why it had taken so long for the Conservatives to have their first openly gay Cabinet minister, the source said: "To be honest, I think the PM, in terms of the Cabinet, appoints people on merit. I don't think he really thinks about issues like that.
"There have been other ministers in the Prime Minister's Government who have been gay. People tend to be appointed on merit and their ability to do the job."