John, or Ioannis (Ἰωάννης) VI Kantakouzenos (Καντακουζηνός) was a Byzantine and Eastern Roman emperor of the late 13th and 14th centuries. He aided Andronikos III take the throne from Andronikos II. He also negotiated with the Genoese after they broke a treaty established by the Nicene Empire and John faced some conflict in which his fleets were destroyed and Galata was burned. He also oversaw the Fifth Council of Constantinople which declared Hesychasm as compatible with Orthodoxy.