What is Whitney Houstons number one selling song?

Whitney Houston's number one selling song is "I Will Always Love You." Originally written and recorded by Dolly Parton, Houston's powerful rendition for the soundtrack of the film "The Bodyguard" became a massive hit, topping charts worldwide. It is widely regarded as one of her signature songs and has sold millions of copies, solidifying her legacy as one of the greatest vocalists in music history.