Nafplio (Modern Greek: Ναύπλιο, Nafplio) is a seaport town in the Peloponnese in Greece that has expanded up the hillsides near the north end of the Argolic Gulf. The town was the first capital of modern Greece, from the start of the Greek Revolution in 1821 until 1834. Nafplio is now the capital of the regional unit of Argolis.

The city was named Nauplia (Ναυπλία) in ancient Greek and Latin. In Ionian Greek, it was also known as Naupliē (Ναυπλιη).

In Byzantine Greek, several variants were used, including Naúplion (Ναύπλιον), Anáplion (Ἀνάπλιον), and Anáplia (Ἀνάπλια). The Turkish name of the town was Mora Yenişehri, after Morea, a medieval name for the Peloponnese, and "yeni şehir," the Turkish for "new city". In Italian, the town was formerly known as Napoli or Napoli di Romania, after the medieval usage of "Romania" to refer to the lands of the Byzantine Empire.

In modern Greek, the town is now called Nafplio (Ναύπλιο), although English continues to employ Nafplion, Navplion, and Nauplia as well.