| Official Name: | Qasr Libya |
| Other Name: | Gasr Elbia[1] |
| Native Name: | قصر ليبيا |
| Settlement Type: | Town |
| Pushpin Map: | Libya |
| Pushpin Label Position: | bottom |
| Pushpin Map Caption: | Location in Libya |
| Subdivision Type: | Country |
| Subdivision Name: |  Libya |
| Subdivision Type1: | Region |
| Subdivision Name1: | Cyrenaica |
| Subdivision Type2: | District |
| Subdivision Name2: | Jabal al Akhdar |
| Population As Of: | 2006 |
| Population Footnotes: | [2] |
| Population Total: | 4,933 |
| Population Blank1 Title: | Ethnicities |
| Population Blank2 Title: | Religions |
| Timezone: | UTC+2 |
| Coordinates: | 32.6333°N 45°W |
Qasr Libya or Qasr Lebia (Arabic: قصر ليبيا, lit. 'Lebia Castle', Lebia/Libya being a corruption of the ancient name Olbia) is a small town in northern Libya about northwest of Bayda. In ancient times, it was called Olbia and Theodorias, the ruins of which were excavated in the 1950s. The town contains a museum with fifty Byzantine mosaics.[3] It's on the cross-roads between the eastwards Marj–Bayda main road, and the southwards Qasr Libya–Marawa road.