Paris Hilton stepped out for a night on the town with her sexy model beau River Viiperi.

The beautiful blonde heiress, wearing a colorful and flowy dress, walked alongside Jeff Beacher ... creator of Beacher's Madhouse at the Roosevelt.

Princess P and River first went public with their romance while attending New York Fashion Week. Since then, the twosome have been inseparable ... even hitting up Magic Mountain for some rollercoaster action.

Looks like Paris and River are lovin' life!