Pausanias (Greek: Παυσανίας) was the Agiad King of Sparta from 445 BC to 426 BC and then from 408 BC to 395 BC. He was the son of the Spartan Agiad king Pleistoanax.
His first reign was as a minor after his father, Pleistoanax, was temporarily deposed and exiled after being charged by the Spartans with taking a bribe, probably from the Athenian leader, Pericles, to withdraw from the plain of Eleusis in Attica after leading the Peloponnesian forces there following the revolts of Euboea and Megara from the Athenian empire. In 426 BC, Pleistoanax was recalled and restored as Agiad King of Sparta and ruled until his death in 409 BC.
Following the Spartan victory over Athens in the Battle of Aegospotami in 405 BC, the Spartans were in a position to finally force Athens to capitulate. Pausanias laid siege to Athens while the Spartan admiral Lysander's fleet blockaded the port city of Piraeus. This action effectively closed the grain route to Athens through the Hellespont, thereby starving Athens. Realising the seriousness of the situation, the Athenian statesman, Theramenes, started negotiations with Lysander. These negotiations took three months, but in the end Lysander agreed to terms at Piraeus. An agreement was reached for the capitulation of Athens and the cessation of the Peloponnesian War in 404 BC.
Lysander then put in place a puppet government in Athens with the establishment of the oligarchy of the Thirty Tyrants under Critias which included Theramenes as a leading member. However, in 403 BC Pausanias was able to undermine Lysander's dominance of Athens after Pausanias gained the command of the Peloponnesian League expedition against the Athenian democrats then based in Piraeus. Despite opposition from Lysander, Pausanias took the opportunity to promote a reconciliation between the democratic party in Piraeus and the oligarchs controlling Athens, thus allowing the reunification of Athens and Piraeus. Pausanias was able to restore democracy in Athens while bringing the Athenians, temporarily, into an alliance with Sparta.