| Election Name: | 1984 United States Senate election in Louisiana |
| Country: | Louisiana |
| Flag Year: | 1912 |
| Type: | presidential |
| Ongoing: | no |
| Previous Election: | 1978 United States Senate election in Louisiana |
| Previous Year: | 1978 |
| Next Election: | 1990 United States Senate election in Louisiana |
| Next Year: | 1990 |
| Election Date: | September 29, 1984 |
| Nominee1: | J. Bennett Johnston |
| Party1: | Democratic Party (United States) |
| Popular Vote1: | 838,181 |
| Percentage1: | 85.75% |
| Nominee2: | Robert M. Ross |
| Party2: | Republican Party (United States) |
| Popular Vote2: | 86,546 |
| Percentage2: | 8.85% |
| Nominee3: | Larry Napoleon Cooper |
| Party3: | Republican Party (United States) |
| Popular Vote3: | 52,746 |
| Percentage3: | 5.4% |
| Map Size: | 300px |
| U.S. Senator | |
| Before Election: | J. Bennett Johnston |
| Before Party: | Democratic Party (United States) |
| After Party: | Democratic Party (United States) |
The primary election for the 1984 United States Senate election in Louisiana was held on September 29, 1984.
Incumbent Democratic Senator J. Bennett Johnston won the election with 85% of the vote and was declared elected by a majority, dispelling the need for a general election in November. This was despite Republican president Ronald Reagan carrying the state with more than 60% of the vote in the concurrent presidential election.
Under Section 511 of Title 18 of the Louisiana Revised Statutes, a candidate who received a majority of the votes in the Primary Election was declared elected. Johnston did not appear on the General Election ballot.[1]