Thessaloniki, Thessalonica or Salonica is Greece's second largest city and the capital of Greek Macedonia, named after Queen Thessalonike of Macedon.

The terms may also refer to:

• Thessaloniki (regional unit) in Greek Macedonia
• Thessalonica of Macedon, the sister of Alexander the Great
• Thessalonica (theme), a province of the Byzantine Empire
• Kingdom of Thessalonica, a Crusader state
• Vilayet of Salonica, a province of the Ottoman Empire