Joannis is a given name. Notable people with the name include:
Joannis Andreou, Greek swimmerJoannis Antonius de Sancto Giorgio, Italian juristJoannis Avramidis, Greek-Austrian sculptorJoannis Capodistrias, Greek politician in RussiaJoannis de Segovia, Spanish theologianJoannis Eschuid, English astrologerJoannis Melissanidis, Greek artistic gymnastJoannis Metaxas, Greek politicianJoannis Phrangoudis, Greek Army officerJoannis Romberch de Kyrspe, WestphaliaJoannis Vislicensis, medieval authorJoanni Perronet, French fencerAndreas Eudaemon-Joannis, Greek Jesuit and philosopherGiovanni Giorgi (composer) (Joannis de Georgiis), Italian composer and priestGiovanni Maria Alemanni, Italian composer and lutenistJan Weenix, Dutch painterJan z Lublina, Polish composer and organistJens Nilssøn (Joannis Nicolai), Bishop of OsloJohann Hedwig, German botanistJohn Martyn (botanist), English botanist