Nicias (/ˈnɪʃiəs/; Νικίας; c. 470 BC – 413 BC), or Nikias, was an Athenian politician and general during the period of the Peloponnesian War. Nicias was a member of the Athenian aristocracy because he had inherited a large fortune from his father, which was invested into the silver mines around Attica's Mt. Laurium. Following the death of Pericles in 429 BC, he became the principal rival of Cleon and the democrats in the struggle for the political leadership of the Athenian state. He was a moderate in his political views and opposed the aggressive imperialism of the democrats. His principal aim was to conclude a peace with Sparta as soon as it could be obtained on terms favourable to Athens.
He was frequently elected to serve as strategos (general) for Athens during the Peloponnesian War. He led several expeditions which achieved little. Nevertheless, he was largely responsible for the successful negotiations which led to the Peace of Nicias in 421 BC.
Following the Peace, he objected to the ambitious plans of Alcibiades for advancing Athens' interests. Despite this, Nicias was appointed to participate in the Athenian invasion of Sicily. The Athenian siege of Syracuse was nearly successful until the arrival of the Spartan general Gylippus, who turned the situation around so that the Athenians were themselves under siege. Nicias led his forces in a desperate attempt to escape by land. However, they were cut off and he and his Athenian army were overwhelmed and defeated. Subsequently, Nicias was executed.