| Election Name: | 1978 United States Senate election in Arkansas |
| Country: | Arkansas |
| Flag Year: | 1924 |
| Type: | presidential |
| Ongoing: | no |
| Previous Election: | 1972 United States Senate election in Arkansas |
| Previous Year: | 1972 |
| Next Election: | 1984 United States Senate election in Arkansas |
| Next Year: | 1984 |
| Election Date: | November 7, 1978 |
| Nominee1: | David Pryor |
| Party1: | Democratic Party (United States) |
| Popular Vote1: | 399,916 |
| Percentage1: | 76.58% |
| Nominee2: | Thomas Kelly Jr. |
| Party2: | Republican Party (United States) |
| Popular Vote2: | 84,722 |
| Percentage2: | 16.22% |
| Nominee3: | John G. Black |
| Party3: | Independent politician |
| Popular Vote3: | 37,488 |
| Percentage3: | 7.18% |
| Map Size: | 200px |
| U.S. Senator | |
| Before Election: | Kaneaster Hodges Jr. |
| Before Party: | Democratic Party (United States) |
| After Election: | David H. Pryor |
| After Party: | Democratic Party (United States) |
The 1978 United States Senate election in Arkansas took place on November 7, 1978. Incumbent U.S. Senator John L. McClellan had died the previous December, leaving the seat vacant. Interim appointee Kaneaster Hodges Jr. did not run to the full seat, and was succeeded by Governor of Arkansas David Pryor.
Pryor won a highly-competitive three-way primary against U.S. Representatives Jim Guy Tucker and Ray Thornton, then defeated Tucker in a run-off election. Having secured the Democratic nomination, which was often tantamount to election in the American South prior to the 1980s, Pryor easily defeated Republican nominee Thomas Kelly and independent candidate John Black.