Ryn [rɨn] (German: Rhein) is a town in northeastern Poland located 19 km (12 mi) southwest of Giżycko, in the Warmian-Masurian Voivodeship, in Masuria.

Grand Master Winrich von Kniprode of the Teutonic Knights built a fortress on the site of a former Old Prussian fortification in 1337.

[1] After the outbreak of the Thirteen Years’ War the castle was captured by the Prussian Confederation, at the request of which in 1454 King Casimir IV Jagiellon signed the act of incorporation of the region to the Kingdom of Poland.

[1] After the Second Peace of Toruń in 1466 it became part of Poland as a fief held by the Monastic State of the Teutonic Knights.

It was not until 1902 that Rhein received a railroad connection, though it was only a one-track link of a light railway with a narrow gauge.

Additionally, the castle was bought and converted into a prison in 1853, and suffered a fire in 1881, after which it was not fully rebuilt until thirty years later.

[5] After Germany's defeat in World War II, the town once again became part of Poland due to the borders changes dictated by the Potsdam Agreement.