The X Factor winner, 33, posted a message on Instagram saying: “My heart is singing the happiest song it’s ever sung!”
Lewis, who added an engagement ring emoji to her post, went on: “I’m bursting with joy and overcome with emotion that I get to embark on this new adventure with my best friend, my partner in crime, my ride or die!
“@dennisjauch I can’t wait to be your wife eeeek wife! What?! Argh!
“Hahahahaha I still can’t believe it. I dreamed you up and you came true."
Specuulation the star had become engaged to her partner of eight years mounted when the former ‘X Factor’ winner subtly showed off a diamond ring in a series of photos and videos posted to Instagram over the summer, although none of her posts actually confirmed the news beyond teasing glimpses of the sparkler.
The couple are notoriously secretive about their private life, and whilst they don’t often talk about their romance, Leona did admit in 2013 that she was looking to settle down with her beau eventually.
She said at the time: “Things with Dennis are going really good.
We haven’t talked about marriage yet. It is something I want to do at some point. I did want to get married in my 20s. That was always a weird thing for me.
“I was always like, ‘I am going to get married in my 20s!’ But now I’m like ‘No, no, no. I’m not ready!’ I feel like you think you are going to be ready but then you get to your late 20s and you’re not ready.”
Leona and Dennis, who began dating in 2010, first met which Dennis worked as a backup dancer during Leona’s tour.