Laconia or Lakonia (Greek: Λακωνία, Lakonía, [lakoˈni.a]) is a historical and administrative region of Greece located on the southeastern part of the Peloponnese peninsula. Its administrative capital is Sparta. The word laconic—to speak in a blunt, concise way—is probably derived from the name of this region, a reference to the ancient Spartans who were renowned for their verbal austerity and blunt, often pithy remarks.

Laconia is bordered by Messenia to the west and Arcadia to the north and is surrounded by the Myrtoan Sea to the east and by the Laconian Gulf and the Mediterranean Sea to the south. It encompasses Cape Malea and Cape Tainaron and a large part of the Mani Peninsula. The Mani Peninsula is in the west region of Laconia. The islands of Kythira and Antikythera lie to the south, but they administratively belong to the Attica regional unit of islands. The island Elafonisos, situated between the Laconian mainland and Kythira, is part of Laconia.

The Evrotas is the longest river in the prefecture. The Evrotas Valley is predominantly an agricultural region that contains many citrus groves, olive groves, and pasture lands. It is the location of the largest orange production in the Peloponnese and probably in all of Greece. Lakonia, a brand of orange juice, is based in Amykles.

The main mountain ranges are the Taygetus 2,407 m (7,897 ft) in the west and the Parnon 1,961 m (6,434 ft) in the northeast. Taygetus, known as Pentadaktylos (five-fingers) throughout the Middle Ages, is west of Sparta and the Evrotas Valley. It is the highest mountain in Laconia and the Peloponnese and is mostly covered with pine trees. Two roads join the Messenia and Laconia prefectures: one is a tortuous mountain pass through Taygetus and the other bypasses the mountain via the Mani district to the south.

The stalactite cave, Dirou, a major tourist attraction, is located south of Areopolis in the southwest of Laconia.

The city of Sparta enjoys a sunny and warm Mediterranean climate (Köppen: Csa). January highs are around 14 °C (57 °F) while July and August highs are around 36 °C (97 °F) in the city proper. Sparta records the highest summer average maximum temperatures in Greece. In July 2012 the city registered an average maximum temperature of 38.3 °C (100.9 °F), making it Greece's second highest monthly average maximum temperature to date after the 38.6 °C (101.5 °F) recorded in Stylida in July 2023. The highest temperature ever recorded in Sparta is 45.7 °C (114.3 °F) in August 2021. On average, Sparta records 5 days per year with temperatures of over 40.0 °C (104.0 °F).

Evidence of Neolithic settlement in southern Laconia has been found during excavations of the Alepotrypa cave site. Significant archaeological recovery exists at the Vaphio-tomb site in Laconia. Found there is advanced Bronze Age art as well as evidence of cultural associations with the contemporaneous Minoan culture on Crete. At the end of the Mycenean period, the population of Laconia sharply declined. In classical Greece, Laconia was Spartan territory but from the 4th century BC onward Sparta lost control of various ports, towns and areas. From the mid-2nd century BC until 395 AD, Laconia was a part of the Roman Empire.

In the medieval period, Laconia formed part of the Byzantine Empire. In the 7th century, Slavic tribes settled in the Peloponnese. Two of them, the Melingoi and the Ezeritai, who settled in parts of Laconia, survived the subsequent Byzantine reconquest and re-Hellenization of the Peloponnese, and are attested until the late Middle Ages.