| Conflict: | Operation Fillmore |
| Partof: | Vietnam War |
| Date: | 26 March – 21 July 1966 |
| Place: | Phú Yên Province, South Vietnam |
| Result: | Inconclusive |
| Combatant1: |  United States |
| Combatant2: | North Vietnam |
| Commander1: | BG Willard Pearson |
| Commander2: | |
| Units1: | 1st Brigade, 101st Airborne Division |
| Units2: | |
| Casualties1: | 8 killed |
| Casualties2: | U.S body count: 134 killed 35 captured |
Operation Fillmore was an operation conducted by the 1st Brigade, 101st Airborne Division in Phú Yên Province, lasting from 26 March to 21 July 1966.[1]
Operation Fillmore was a continuation of the harvest security operations of Operation Harrison.[1]
The 1st Battalion, 327th Infantry Regiment was retained as a reserve force at Tuy Hoa Air Base, while the 2/327th Infantry and the 2nd Battalion, 502nd Infantry Regiment patrolled the rice-growing plains and the western foothills.[1]
In early April, 2/502nd Infantry was rotated to Tuy Hoa Air Base and 1/327th and 2/327th began a block and sweep operation in the mountains northwest of Tuy Hòa. On 7 April a company from 1/327th engaged an entrenched company-sized force, killing 28 defenders.[1]
Given that the PAVN had apparently withdrawn from the Tuy Hòa Valley, on 9 April 1/327th and 2/502nd were redeployed, leaving only the 2/327th Infantry to continue operations.[1]
Operation Fillmore officially concluded on 21 July, the US claimed PAVN losses were 134 killed and 35 captured, U.S. losses were 8 killed.[1]