| Image Coa: | DEU Diethardt COA.svg |
| Coordinates: | 50.1639°N 7.8747°W |
| Image Plan: | Diethardt in EMS.svg |
| State: | Rheinland-Pfalz |
| District: | Rhein-Lahn-Kreis |
| Verbandsgemeinde: | Nastätten |
| Elevation: | 300 |
| Area: | 4.42 |
| Postal Code: | 56355 |
| Area Code: | 06772 |
| Licence: | EMS, DIZ, GOH |
| Gemeindeschlüssel: | 07 1 41 502 |
| Divisions: | 2 |
| Website: | www.diethardt.de |
| Mayor: | Kerstin Reek-Berghäuser[1] |
| Leader Term: | 2019 - 24 |
Diethardt is a municipality in the district of Rhein-Lahn, in Rhineland-Palatinate, in western Germany.