The 29-year-old blogger was a familiar face to many, having made appearances on shows like Come Dine With Me, where he emerged the winner.
His devastated loved ones have paid tribute to the Coronation Street superfan, who had a Deirdre Barlow tattoo on his ankle.
Mr Hett’s boyfriend, Russell Hawyward, wrote on Twitter: “We got the news last night that our wonderful, iconic and beautiful Martyn didn’t survive.
“He left the world exactly how he lived, centre of attention. I’m in a really bad way so please forgive if I don’t reply.
“Thankfully I have his wonderful and amazing friends to keep each other strong. I love you Martyn. I always will.”
His brother, Dan Hett, added: “They found my brother last night. We are heartbroken.”
Mr Hett was with friend Stuart Aspinell at the Ariana Grande concert on Monday night before they were separated.
He was reported missing until news of his death was confirmed this morning – on the week he was due to go on a two-month trip to the United States.
Mr Hett’s kindness was highlighted last year when he tweeted about his mum not selling any of her craft work at a Christmas fair.
Alongside details of her online shop, he wrote: “My mum has set up her own stall at a craft fair and has messaged me to say she hasn’t sold anything yet and my heart is breaking.”
When the story went viral on Twitter, people soon started buying his mum’s products, before she eventually sold out.
Mr Hett later posted a picture of his smiling mother, writing: “Omg she’s bought this book to help her cope with her new followers/fanbase on twitter I just love her.”
His devastated friends spoke about how inspiring he was to them.
One wrote: “I’ve never met someone who lived their life as fully as he did, he was fearless and confident in such an inspiring way.
“I want our national anthem replaced with his cackle. Not many people can leave a legacy as strong as he did just by being himself. He was as he always said, iconic.”
Soulmate doesn’t even come close. Come back to us Martyn so we can watch last nights Corrie together ???? pic.twitter.com/cXbehUgoxc
— ????Russell (@RussellHayward) May 23, 2017
Mark Holbrook added: “It was immediately plain to see to anyone who met him he was a vibrant, exciting and fun loving person and the life of any occasion.”
Schoolgirls as young as eight and parents who had come to pick up their children were also among those killed in the suicide bomb attack.
The youngest person known to have died is eight-year-old Saffie Roussos, who was at the concert with her mother.
Another young victim is thought to be schoolgirl Megan Hurley.
Top pic: Twitter