| Frederick I, Duke of Brunswick-Osterode | |
| House: | House of Guelph |
| Father: | Ernest I, Duke of Brunswick-Grubenhagen |
| Mother: | Adelaide of Everstein-Polle |
| Spouse: | Adelaide of Anhalt-Zerbst |
| Issue: | Otto II, Duke of Brunswick-Osterode |
| Death Date: | 1421 |
Frederick I, Duke of Brunswick-Osterode (-1421) was a son of Duke Ernest I and his wife, Adelaide of Everstein-Polle.
In 1361, he succeeded his father as Count of Osterode.
He married Adelaide (d. before 1421), a daughter of Bernhard V, Prince of Anhalt-Bernburg, and was the father of Otto II (1396-1452), who succeeded him. He may have also married Elizabeth, heiress of Homburg.