John VII Grammatikos or Grammaticus, i.e., 'the Grammarian' (Greek: ??峎彖彖庢? ?? ??帢弮弮帢?庣庥??, I?ann?s VII Grammatikos), Ecumenical Patriarch of Constantinople from January 21, 837 to March 4, 843, died before 867.

John was renowned for his learning (hence the nickname Grammatikos), and for his persuasive rhetoric in the endless debates that are a favorite subject of hagiographic sources reflecting the second period of Iconoclasm. John was also charged with tutoring the future Emperor Theophilos during the reign of his father Michael II, and is credited with instilling strong Iconoclast sympathies in his student. On the accession of Theophilos, John was appointed synkellos (patriarch's assistant), a position that made him a likely heir to the patriarchate.

In c. 830, John was dispatched on an embassy to the Caliph al-Ma'mun, but this did little to prevent a period of fierce warfare between the Byzantine Empire and the Abbasids. He did, however, bring back a plan of the Abbasid palace at Baghdad for the amusement of his emperor and supervised the building of a similar structure in Bithynia.

The circumstances of John VII's patriarchate are obscure. He was appointed patriarch by his student Theophilos and may have been responsible for the slight intensification of the persecution of Iconodules. He was deposed by Theophilos' widow Theodora (his own relative) as a preliminary towards the ending of Iconoclasm in 843. The deposed patriarch survived into the 860s.