Johann von Mengede (also Johann von Mengden, called Osthof) (c. 1400 — 15 August 1469) was a knight of the Teutonic Knights. Most notably, from 1442 to 1450, he was Komtur of Reval and then from 1450 to 1469 a Master (Landmiester) of the Livonian Order. He was elected as the Landmaster of Livonia in April, 1450. He is the best known representative of the Brandenburg noble family from Mengede.