The Twilight actress sounded super loved up as she gushed about her gorgeous fiancée in a new interview with Us Weekly.
It marked the first confirmation of their engagement.
Nikki said: "He's so beautiful inside and out! He's quite possibly the most amazing man that's ever walked the planet. It's crazy. I'm so lucky. I love him!"
The couple were friends before romance blossomed last year. Their relationship was first revealed during the summer when they were pictured putting on a PDA in New York.
Engagement rumours surfaced earlier this month.
A source told E! News: "They're so happy. They were crazy happy from the start. Their families love each other. It just feels really right."
While Nikki says she's "so lucky" to have found Ian, the Vampire Diaries star has been equally open in his admiration and love for her.
Back in September, Ian hit back at critical comments about Nikki online, saying: "She is a compassionate and beautiful human being." He also called her "magical."
This will be Ian's first wedding. Nikki was previously married to American Idol contestant Paul McDonald.
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