Athens ( ATH-inz; Greek: Αθήνα, romanized: Athína [aˈθina] (listen); Ancient Greek: Ἀθῆναι, romanized: Athênai (pl.) [atʰɛ̂ːnai̯]) is the capital and largest city of Greece. Athens dominates the Attica region and is one of the world's oldest cities, with its recorded history spanning over 3,400 years and its earliest human presence beginning somewhere between the 11th and 7th centuries BC.Classical Athens was a powerful city-state. It was a centre for the arts, learning and philosophy, and the home of Plato's Academy and Aristotle's Lyceum. It is widely referred to as the cradle of Western civilization and the birthplace of democracy, largely because of its cultural and political impact on the European continent—particularly Ancient Rome. In modern times, Athens is a large cosmopolitan metropolis and central to economic, financial, industrial, maritime, political and cultural life in Greece. In 2021, Athens' urban area hosted more than three and a half million people, which is around 35% of the entire population of Greece.

Athens is a Beta global city according to the Globalization and World Cities Research Network, and is one of the biggest economic centers in Southeastern Europe. It also has a large financial sector, and its port Piraeus is both the largest passenger port in Europe, and the third largest in the world.The Municipality of Athens (also City of Athens), which actually constitutes a small administrative unit of the entire city, had a population of 664,046 (in 2011) within its official limits, and a land area of 38.96 km2 (15.04 sq mi). The Athens Urban Area or Greater Athens extends beyond its administrative municipal city limits, with a population of 3,090,508 (in 2011) over an area of 412 km2 (159 sq mi). Athens is also the southernmost capital on the European mainland and the warmest major city in Europe.

The heritage of the Classical Era is still evident in the city, represented by ancient monuments, and works of art, the most famous of all being the Parthenon, considered a key landmark of early Western civilization. The city also retains Roman and Byzantine monuments, as well as a smaller number of Ottoman monuments, while its historical urban core features elements of continuity through its millennia of history. Athens is home to two UNESCO World Heritage Sites, the Acropolis of Athens and the medieval Daphni Monastery. Landmarks of the modern era, dating back to the establishment of Athens as the capital of the independent Greek state in 1834, includes the Hellenic Parliament and the so-called "Architectural Trilogy of Athens", consisting of the National Library of Greece, the National and Kapodistrian University of Athens, and the Academy of Athens. Athens is also home to several museums and cultural institutions, such as the National Archeological Museum, featuring the world's largest collection of ancient Greek antiquities, the Acropolis Museum, the Museum of Cycladic Art, the Benaki Museum, and the Byzantine and Christian Museum. Athens was the host city of the first modern-day Olympic Games in 1896, and 108 years later it hosted the 2004 Summer Olympics, making it one of the few cities to have hosted the Olympics more than once.