John I of Brunswick-Grubenhagen

John I of Brunswick-Grubenhagen (c. 1304 – 23 May 1367) was a younger son of Duke Henry I the Miraculous and Agnes of Meissen. Destined for the church, he entered the Mainz cathedral chapter in 1320 and in 1325 surrendered his inheritance to his brothers Henry II, Ernest I and William for a pension of thirty marks a year.

He held church dignities at Hildesheim, Osnabrück and Münster, was cathedral provost of Halberstadt from 1341, and later provost of St. Alexandri in Einbeck, where he died and was buried in 1367.