This is a list of films which placed number one at the weekly box office in the United States during 1940 per Variety s weekly National Boxoffice Survey. The results are based on a sample of 20-25 key cities and therefore, any box office amounts quoted may not be the total that the film grossed nationally in the week.
| † | This implies the highest-grossing movie of the year. |
| Date | Title | Ref |
|---|---|---|
| January 3 | Mr. Smith Goes to Washington | [1] |
| January 10 | [1] | |
| January 17 | [1] | |
| January 24 | The Grapes of Wrath | [1] |
| January 31 | Gone with the Wind | [1] |
| February 7 | [2] | |
| February 14 | [2] | |
| February 21 | [2] | |
| February 28 | [2] | |
| March 6 | Pinocchio | [3] |
| March 13 | [3] | |
| March 20 | [3] | |
| March 27 | [3] | |
| April 3 | [4] | |
| April 10 | The Grapes of Wrath | [4] |
| April 17 | Rebecca † | [4] |
| April 24 | Pinocchio | [4] |
| May 1 | The Grapes of Wrath | [5] |
| May 8 | [5] | |
| May 15 | [5] | |
| May 22 | [5] | |
| May 29 | [5] | |
| June 5 | [6] | |
| June 12 | [6] | |
| June 19 | [6] | |
| June 26 | His Girl Friday | [6] |
| July 3 | The Grapes of Wrath | [7] |
| July 10 | [7] | |
| July 17 | [7] | |
| July 24 | His Girl Friday | [7] |
| July 31 | [7] | |
| August 7 | The Grapes of Wrath | [8] |
| August 14 | [8] | |
| August 21 | [8] | |
| August 28 | [8] | |
| September 4 | [9] | |
| September 11 | [9] | |
| September 18 | [9] | |
| September 25 | [9] | |
| October 2 | [10] | |
| October 9 | [10] | |
| October 16 | Boom Town | [10] |
| October 23 | North West Mounted Police | [10] |
| October 30 | [10] | |
| November 6 | [11] | |
| November 13 | [11] | |
| November 20 | Fantasia | [11] |
| November 27 | [11] | |
| December 4 | [12] | |
| December 11 | [12] | |
| December 18 | [12] | |
| December 25 | [12] |