| John Day | |
| State House: | Indiana |
| State: | Indiana |
| District: | 100th |
| Term: | 1996 – 2012 |
| Succeeded: | Dan Forestal |
| Party: | Democratic |
| Birth Name: | John Joseph Day |
| Birth Date: | 25 August 1937 |
| Birth Place: | Indianapolis, Indiana |
| Alma Mater: | Marian College, Indiana University |
| Occupation: | Educator |
| Spouse: | Mary Jo Thomas-Day |
| Residence: | Indianapolis, Indiana |
John Joseph Day (born August 25, 1937) is a former Democratic member of the Indiana House of Representatives, representing the 100th District from 1996 until 2012. He previously served from 1974 through 1994.