| Osterburg | |
| Native Name: | The fortified house at Weida |
| Built: | 1163 to 1193 |
| Type: | hill castle |
| Condition: | preserved or largely preserved |
| Location: | Weida |
| Coordinates: | 50.7726°N 12.0568°W |
| Map Type: | Thuringia#Germany |
| Code: | DE-TH |
The Osterburg (pronounced as /de/) is a castle located conspicuously on a hill in the middle of the town of Weida in the county of Greiz in the German state of Thuringia.
Its 54-metre-high bergfried is the third highest and one of the oldest surviving bergfrieds in Germany. Above its second array of battlements there is a watchman's parlour, which accommodated a watchman until 1917. On the terrace there is a monument which records that this was the furthest south that the ice sheet came in Germany during the Elster glaciation.