Ioannis or Ioannes , shortened to Giannis or Yannis (Γιάννης) is a Greek given name, the origin of Johannes and John. Notable people with the name include:

• Ioannis Alevras, Greek politician
• Ioannis Amanatidis, Greek footballer
• Ioannis Bourousis, Greek basketball player
• Ioannis Drymonakos, Greek swimmer
• Ioannis Gagaloudis, Greek basketball player
• Ioannis Kakridis (1901–1992), Greek classical scholar
• Ioannis Kalitzakis, Greek footballer
• Ioannis Kapodistrias (John Capodistrias), Greek politician in Russia
• Ioannis Kasoulidis, Cypriot politician
• Ioannis Kolettis (1773–1847), Greek politician who served as Prime Minister of Greece
• Ioannis Metaxas, Greek general and politician
• Ioannis Okkas, Cypriot football player
• Ioannis Paraskevopoulos, Greek banker and politician
• Ioannis Plagis (John Plagis), Southern Rhodesian flying ace during World War II
• Ioannis Rallis, Greek politician
• Ioannis Samaras, Greek footballer
• Ioannis Tamouridis, Greek cyclist
• Ioannis Theofilakis, Greek shooter
• Ioannis Theotokis (1880–1961), Greek politician who became Prime Minister of Greece
• Ioannis Varoufakis - commonly known as Yanis Varoufakis, Greek politician