| Fljótsdalshérað | |
| Settlement Type: | Former municipality |
| Mapsize: | 250px |
| Pushpin Map: | Iceland |
| Coordinates: | 65.264°N -14.395°W |
| Subdivision Type: | Country |
| Subdivision Name: | Iceland |
| Subdivision Type1: | Region |
| Subdivision Name1: | Eastern Region |
| Subdivision Type2: | Constituency |
| Subdivision Name2: | Northeast Constituency |
| Subdivision Type3: | Municipality |
| Subdivision Name3: | Múlaþing |
| Leader Title: | Mayor |
| Leader Name: | Björn Ingimarsson |
| Unit Pref: | Metric |
| Area Total Km2: | 8,884 |
| Population As Of: | 2018 |
| Population Total: | 3,580 |
| Population Density Km2: | auto |
| Postal Code Type: | Postal code(s) |
| Postal Code: | 700, 701 |
Fljótsdalshérað (pronounced as /is/) was a municipality located in eastern Iceland. In 2020 it merged with three neighbouring municipalities to form Múlaþing.