Blake Shelton thinks the idea of Gwen Stefani being his fiancee is "ridiculous".

Gwen Stefani and Blake Shelton

Gwen Stefani and Blake Shelton

The 44-year-old singer - who got engaged to the 'Hollaback Girl' hitmaker last October after five years together - admitted his younger self wouldn't believe the way his life has turned out and the fact they're a couple still makes him laugh because they are such an unlikely couple.

He said: "If you would have told me back in 1996 that Gwen Stefani was gonna be my girlfriend, I would have laughed you out of the room.

"You know what I'm saying? I would have thought you were crazy. Saying it right now, I almost bust out laughing. That's how ridiculous it is."

The 'God's Country' hitmaker admitted meeting Gwen is still the "greatest thing" that has happened to him in his 10 years on 'The Voice'.

During the 'Road to Lives - 10th Anniversary Edition' special of the talent show, he said: "People ask me all the time, 'What's the greatest thing that has happened for you since you've been on 'The Voice'?'

"That's a no-brainer, right? I met my fiancée here. It's hard to resist Gwen Stefani. You know, here's this iconic rock star coming to be a coach on 'The Voice' in a black minivan. That was cool to me."

Blake - who was previously married to Miranda Lambert - admitted having Gwen seated alongside him on the panel of the show brings in a "very complicated element of competition" but he's thrilled that she just adds to the "challenge" of wanting the hopefuls he mentors to win.

He added: "I love it when she's here. She brings a very complicated element of competition, for me in particular. But I love that. I love the challenge. Just knowing that she's there, and she has my back, is pretty cool."