Miley Cyrus' Obsessed Fan Arrested in Vegas, Wanted to Impregnate Her

Miley Cyrus' iHeartRadio set in Las Vegas nearly took a dark turn due to a man cops say is obsessed with knocking her up -- and it was only her eagle-eyed bodyguards who prevented disaster.

Law enforcement sources tell TMZ ... cops were called to the T-Mobile Arena Saturday night after Miley's security team noticed 42-year-old David Rumsey in the audience. We're told Rumsey was on their watch list because he'd allegedly made previous threats against her.

Our sources say Rumsey told Miley's team, "It's my life's mission to impregnate Miley." We're told the guy also claimed he was going to raise Michael Jackson and Prince from the dead so they could party with him and Miley.

After being detained by Miley's security team, Rumsey was arrested and booked into the Clark County Jail on a felony charge of making threats. He is still currently in custody.

The guy's Twitter feed is frighteningly bizarre. In tweets the week before the concert he tells Miley he's sorry for hurting her and blames Donald Trump. Then he insinuates that after they meet in Vegas they'll be able to party with MJ, Prince and Tupac.

Sources tell us those twisted tweets are why Miley's team had distributed Rumsey's photo to staff inside the venue and instructed them to be on the lookout during her performance.

Mission accomplished for Team Miley.