Singers Blake Shelton and Gwen Stefani Picture: Bang Showbiz

According to a source close to the couple, Blake Shelton calls Gwen Stefani the "unicorn of girlfriends".

The 41-year-old musician has been dating the blonde beauty since 2015, and he considers himself to be a very lucky man, even comparing Gwen to the mythical creature.

A source explained: "Blake jokes with Gwen that she is so hot, and so down to Earth that she is like the unicorn of girlfriends ... women like her shouldn't exist in the real world."

Blake is already convinced Gwen is the perfect woman for him, with an insider revealing he would love to marry the chart-topping star.

The source told HollywoodLife.com: "Blake knows too that if you find yourself lucky enough to be dating someone like Gwen, you marry her. Gwen is marriage material, for sure."

In June, Blake admitted things are "really good" between himself and Gwen.

The 'Came Here To Forget' hitmaker said the pair couldn't be happier together.

He shared: "She's [doing] great. She's sad that 'The Voice' is over, she loves doing the show ... Well, I hope she's good with me!

"I'm real good with her. We're just content and happy and it's just - it's an incredible feeling. Our hobby is just hanging out together, you know? She's my best friend."

Blake also revealed he loves having Gwen by his side because it "builds his ego up".

However, he also admitted to being overshadowed by the 47-year-old star, who was previously married to English musician Gavin Rossdale.

He explained: "Oh my God, at some point, it kinda builds your ego up when you walk into a room with Gwen.

"But also it's a crashing blow to your ego when you realise all the cheers and people shouting at you. You realise it's not you, it's her! But it's still exciting at the same time. Being in the vicinity of her is unbelievable."a