Megara (Greek: Μέγαρα) is an ancient city in Attica, Greece, on the Saronic Gulf opposite the island of Salamis, which belonged to Megara in archaic times, before being taken by Athens. Megara was one of the four districts of Attica, embodied in the four mythic sons of King Pandion, of whom Nisos was the ruler of Megara.

In historical times, colonists from Megara (c. 667 BC) founded Byzantium, as well as Chalcedon and, in Sicily, Megara Hyblaea, a small polis north of Syracuse. The most famous citizen of Megara in antiquity was Euclid. The 6th-century poet Theognis also came from Megara. The Megarans were proverbial for their generosity in building and endowing temples. Jerome, in 409 AD. (letter cxxiii.15 [1]  (http://www.ccel.org/fathers/NPNF2-06/letters/lette123.htm)) reports "There is a common saying about the Megarians... "They build as if they are to live forever; they live as if they are to die tomorrow."

In the Peloponnesian War (c. 431 BC-404 BC), Megara was an ally of Sparta.

Today, Megara is a suburb of Athens. 30,000 people live within the municipality. It is located 42 km WNW of Athens, and is linked by a highway connecting the Peloponnese, Western Greece, and Athens. It will now be linked by a high-speed rail line. Megara is a town lying in the Megaris plain, and much of the municipality is in this plain. Agriculture used to dominate before houses began developing in Megara in the 1960s and the 1970s. 3 km south is a small community lying about less than 1 km north of the island of Salamis, called Pachi. The population is small. There is a bridge (to some residents) that will connect the island with the mainland, but is not yet planned. Neos Peramos is the neighboring city to the east and Kakia Skala to the west. The area also has an military airport in the east northeast. South of the city is the Megara Bay.