Camping within Zion National Park is not free. There are three campgrounds within the park: South Campground, Watchman Campground, and Lava Point Campground. Both South and Watchman Campgrounds require fees for camping, while Lava Point Campground is free but operates on a first-come, first-served basis and is often full due to its limited availability (only six primitive campsites).
Outside of the park, you can find dispersed camping on nearby Bureau of Land Management (BLM) land, which is typically free. However, these sites are primitive and have no facilities, so you'll need to come prepared. For more camping options near Zion, consider these sites: