Risotto does have a rice gluten in it.
However the gluten that the risotto has in it is not the same gluten that bothers someone with a gluten intolerance.
If you have a gluten intolerance then you can usually eat risotto without any issues.
I'm gluten intolerant myself and can eat risotto even though it has a different type of gluten in it.
You can also make homemade risotto and use ingredients that contain no gluten and that would mean that the risotto you make is entirely gluten free.
The high rice gluten content in the Arborio rice gives the risotto the creamy, rich consistency and texture it has.
But since it's a different type of gluten those with gluten intolerance can eat risotto without having any issues.