There are several fantastic options for islands near Athens that are perfect for a day trip. They are mostly located in the Saronic Gulf and are easily accessible by the high-speed ferry catamaran from the port of Piraeus, or by powerboats.
Here are the top recommendations, with estimated travel times:
Top Day Trip Islands from Piraeus (Athens' Port)
Aegina: Closest and most popular. Known for the Temple of Aphaia, beautiful port town, and its famous pistachios.40 minutes
Agistri: Small, quiet, and very green, with beautiful beaches and clear waters. Great for relaxing or cycling.50 - 55 minutes
Moni: Small non inhabited island, full of wildlife, deers, peacocks, squirrel. Very close to Aegina, accessible by small boats from Perdika village.
Hydra: Famous aristocratic, car-free island. Beautiful stone mansions, elegant harbor, and you get around by foot or donkey/water taxi.1 hour 20 minutes
Poros: Green island with a picturesque town built amphitheatrically around the port. Separated from the Peloponnese by a narrow strait.1 hour 5 minutes.
Other Options
Kea (Tzia): Closer to the mainland, but you depart from the port of Lavrio (about an hour's drive from Athens). It's a quieter Cycladic island with a rich history and hiking trails. About 1 hour (from Lavrio).
Kythnos (also sometimes called Thermia) is a beautiful Greek island in the Cyclades archipelago, known for its authentic, laid-back atmosphere, thermal springs, and unique beaches. About 1 and a half hour from Lavrio.
Day Cruises: You can also book a popular 3-Island Cruise that typically visits Aegina, Moni, Agkistri or Hydra, Poros, and Aegina in one long day. This allows you to get a taste of all three, though you'll have limited time on each.
Important Tip: Always check the latest ferry schedules and book your tickets in advance, especially if you plan to travel on a weekend or during the peak summer season, as travel times and frequency can vary. If you have the budget, also consider a private boat tour on a powerboat.