| John I, Duke of Brunswick-Grubenhagen | |
| House: | House of Guelph |
| Father: | Henry I, Duke of Brunswick-Lüneburg |
| Mother: | Agnes of Meissen |
| Birth Date: | before 1322 |
John I, Duke of Brunswick-Grubenhagen (born: before 1322; died: 23 May 1367) was provost of the St. Alexandri Minster in Einbeck.
He was the son of Duke Henry I "the Marvelous" of Brunswick-Grubenhagen and his wife Agnes of Meissen, daughter of Margrave Albert II of Meissen.