| Election Name: | 1940 United States Senate election in Pennsylvania |
| Country: | Pennsylvania |
| Type: | presidential |
| Ongoing: | no |
| Previous Election: | 1934 United States Senate election in Pennsylvania |
| Previous Year: | 1934 |
| Next Election: | 1946 United States Senate election in Pennsylvania |
| Next Year: | 1946 |
| Election Date: | November 5, 1940 |
| Image1: | Joseph Guffey.jpg |
| Nominee1: | Joseph F. Guffey |
| Party1: | Democratic Party (US) |
| Popular Vote1: | 2,069,980 |
| Percentage1: | 51.79% |
| Nominee2: | Jay Cooke |
| Party2: | Republican Party (US) |
| Popular Vote2: | 1,893,104 |
| Percentage2: | 47.36% |
| Map Size: | 240px |
| U.S. Senator | |
| Before Election: | Joseph F. Guffey |
| Before Party: | Democratic Party (US) |
| After Election: | Joseph F. Guffey |
| After Party: | Democratic Party (US) |
The 1940 United States Senate election in Pennsylvania was held on November 5, 1940. Incumbent Democratic U.S. Senator Joseph F. Guffey successfully sought re-election to another term, defeating the Republican nominee, Jay Cooke.
As of 2023, this is the last time that Mifflin County and Montour County voted Democratic in a Senate election. This was also the last time until 1991 that Democrats won this Senate seat, and the last until 2006 that they were elected to this seat for a full term.
|-|-bgcolor="#EEEEEE"| colspan="3" align="right" | Totals| align="right" | 3,997,020| align="right" | 100.00%| align="right" | |}