Adam Lambert and Boyfriend Oliver Gliese Split After Over 3 Years Together

Adam Lambert is back on the market ... 'cause TMZ has learned the singer and his longtime boyfriend have quietly gone their separate ways.

Sources with direct knowledge tell TMZ ... the "American Idol" alum and Oliver Gliese broke up within the last month -- and we're told it was an amicable, clean, drama-free split.

Our sources say the romance fizzled out naturally after more than three years together.

Lambert and Gliese first got together in February 2021, and by May of that year, they were publicly showing off their love -- traveling the globe, hitting red carpets, and showing up on red carpets together.

Gliese hails from Denmark and works in the fashion world ... and was frequently seen cheering Adam on at his performances and premieres.