Athens ( ATH-inz; Greek: Αθήνα, romanized: Athína [aˈθina] (listen); Ancient Greek: Ἀθῆναι, romanized: Athênai (pl.) [atʰɛ̂ːnai̯]) is a major coastal urban area in the Mediterranean and is both the capital and largest city of Greece. With its surrounding urban area's population numbering over three million, it is also the eighth largest urban area in the European Union. Athens dominates and is the capital of 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 millennia BCE.

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 influence 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 2023, Athens' surrounding metropolitan area had a population of 3.1 million.

Athens is a Beta-status 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 3rd busiest passenger port in Europe, and the 26th largest container port in the world.

The Municipality of Athens (also City of Athens), which actually constitutes a small administrative unit of the entire urban area, had a population of 643,452 (in 2021) within its official limits, and a land area of 38.96 km² (15.04 sq mi). The Athens Metropolitan Area or Greater Athens extends beyond its administrative municipal city limits, with a population of 3,744,059 (in 2021) 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 continental Europe with an average annual temperature of up to 19.8 °C (67.6 °F) locally.

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, Byzantine and 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, include 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. Athens joined the UNESCO Global Network of Learning Cities in 2016.