| Type: | Ortsteil |
| Municipality: | Südeichsfeld |
| Image Coa: | wappen Lengenfeld unterm Stein Germany.jpg |
| Coordinates: | 51.2147°N 10.2217°W |
| State: | Thüringen |
| District: | Unstrut-Hainich-Kreis |
| Elevation: | 260 |
| Area: | 13.34 |
| Population: | 1246 |
| Stand: | 2010-12-31 |
| Postal Code: | 99976 |
| Area Code: | 036027 |
| Website: | l-u-st.de |
Lengenfeld unterm Stein (or Lengenfeld/Stein) is a village and a former municipality in the Unstrut-Hainich-Kreis district of Thuringia, Germany. Since 1 December 2011, it is part of the municipality Südeichsfeld.