This is a list of singles that reached number one on the Cash Box Top 100 Singles chart in 1991, presented in chronological order.
| Indicates best-performing single of 1991 |
| Issue date | Song | Artist | |
|---|---|---|---|
| January 5 | "Justify My Love" | Madonna | |
| January 12 | |||
| January 19 | |||
| January 26 | "Love Will Never Do (Without You)" | Janet Jackson | |
| February 2 | "The First Time" | Surface | |
| February 9 | "Gonna Make You Sweat (Everybody Dance Now)" | C+C Music Factory featuring Freedom Williams | |
| February 16 | |||
| February 23 | "All the Man That I Need" | Whitney Houston | |
| March 2 | |||
| March 9 | "One More Try" | Timmy T | |
| March 16 | "Someday" | Mariah Carey | |
| March 23 | |||
| March 30 | "Coming Out of the Dark" | Gloria Estefan | |
| April 6 | |||
| April 13 | "I've Been Thinking About You" | Londonbeat | |
| April 20 | "Baby Baby" | Amy Grant | |
| April 27 | |||
| May 4 | |||
| May 11 | "Joyride" | Roxette | |
| May 18 | "Here We Go" | C + C Music Factory Featuring Freedom Williams & Zelma Davis | |
| May 25 | "Rhythm of My Heart" | Rod Stewart | |
| June 1 | "I Don't Wanna Cry" | Mariah Carey | |
| June 8 | "More Than Words" | Extreme | |
| June 15 | |||
| June 22 | "Rush Rush" | Paula Abdul | |
| June 29 | |||
| July 6 | |||
| July 13 | "Unbelievable" | EMF | |
| July 20 | |||
| July 27 | "Right Here, Right Now" | Jesus Jones | |
| August 3 | bgcolor=#FFFF99 rowspan="6" | "(Everything I Do) I Do It for You" | Bryan Adams |
| August 10 | |||
| August 17 | |||
| August 24 | |||
| August 31 | |||
| September 7 | |||
| September 14 | "The Promise of a New Day" | Paula Abdul | |
| September 21 | |||
| September 28 | "I Adore Mi Amor" | Color Me Badd | |
| October 5 | |||
| October 12 | "Emotions" | Mariah Carey | |
| October 19 | |||
| October 26 | "Romantic" | Karyn White | |
| November 2 | |||
| November 9 | "Can't Stop This Thing We Started" | Bryan Adams | |
| November 16 | "Cream" | Prince and the New Power Generation | |
| November 23 | |||
| November 30 | "When a Man Loves a Woman" | Michael Bolton | |
| December 7 | |||
| December 14 | "It's So Hard to Say Goodbye to Yesterday" | Boyz II Men | |
| December 21 | |||
| December 28 | "Black or White" | Michael Jackson |