Troezen (/ˈtriːzən/; Greek: Τροιζήν, modern: Τροιζήνα Troizina) is a small town and a former municipality in the northeastern Peloponnese, Greece. Since the 2011 local government reform it is part of the municipality Troizinia, of which it is a municipal unit.
Troezen is located southwest of Athens, across the Saronic Gulf, and a few miles south of Methana. The seat of the former municipality (pop. 6,507) was in Galatas. Troizina was part of Piraeus Prefecture (in antiquity it was part of Argolis). The municipality had a land area of 190.697 km². Its largest towns and villages are Galatás (pop. 2,592 in 2001), Kalloní (pop. 751), Troizína (pop. 671), Taktikoúpoli (391), Karatzás (350), Dryópi (318), Ágios Geórgios (284), and Agía Eléni (227). There are numerous smaller settlements.