"Deep Inside" is a song by American R&B singer-songwriter Mary J. Blige. It was third single released in the United Kingdom from her fourth album, Mary, and the second single from the album in the United States. Like the preceding single, "All That I Can Say", it was a moderate success in the United States peaking at number fifty-one on the BillboardHot 100, seven places lower than the previous single. In the United Kingdom, however, it was one of her least successful singles to date and Blige's first single to miss the UK top 40 since the first release of "Real Love" seven years earlier. The song features Elton John, who plays elements of his song "Bennie and the Jets" on the piano, which "Deep Inside" samples. He does not provide additional vocals. The video for the single features Blige and her dancers performing to "Sincerity", which appears on the deluxe edition of the Mary album in the United States and the United Kingdom single of "Deep Inside."
The music video was shot on October 8, 1999 in New York City and was directed by Marcus Raboy. An alternate version of the music video features Elton John playing the piano. In the beginning, Blige steps in the stage with her "Takeover Master of Hip-Hop Soul" pose wearing a blonde glitter dress and the screen fades out flashing back all of the music videos that starred Blige herself. The music videos were "Love Is All We Need", "Seven Days", "Everything", "Be Happy", "I'm Goin' Down", "You Bring Me Joy", "Real Love" and "I Can Love You". The next scene begins with two security guards blocking the red carpet and Blige begins singing with her feeling. When the first verse was over, she stands out on the red carpet waving her hands at the whole audience taking pictures of Blige. She steps inside the tour bus looking in the mirror at herself pushing her hand singing the hook. On the next scene, she looks at the audience with green and blue eyes being angry and Blige becomes scared at them within her heart. She walks out of a 1997 Dodge Caravan talking off a hoodie being exposed. Then, she walks ten steps away from an electrical fence with a bronze-raccoon coat and a white tank. She stands over at a Harlem neighborhood with the Manhattan Bridge mocking her and standing 15 feet away from Blige. Then, the next scene starts with black-suited dancers and Blige herself with a red suit dancing to an unreleased track, "Sincerity". After the song ends, They clearly dance to "Deep Inside" and Blige was not dancing but singing loudly all by herself alone. Blige looks at the screen screaming her quote "MJB" at the end of the song, where the Manhattan Bridge is shown. The video premiered on November 10, 1999 on MTV during a season finale of the adults-only animated TV show, Beavis and Butt-head.