A man camped outside Katy Perry's house for two hours over the weekend and just stood there -- staring at the house before her security team eventually called the cops.

According to law enforcement sources, officers showed up on the scene and gave the guy a talking to. They then sent him on his way. Katy wasn't even at home.

And really, if he wanted her to like him, he could have done SOMETHING while he was there. Weed the garden maybe?

Here's a better view of Katy - in her new Adidas commercial.