Minimum age to book and stay in a hotel in Paris?

I was wondering what the minimum age was for booking and staying in a hotel in Paris. I heard it was 19, but some sites are confusing me. Can anybody help?
You see, I heard it was the law in France, or at least Paris, to be 19 to book or stay in a hotel with adult supervision. Could somebody prove me wrong please! My friends and I are racing from Big Ben to the top of the Eiffel Tower in August and need to sort a hotel out for a night. Thanks for the answers!