Rezi Castle, Medieval castle ruin in Rezi, Hungary.

Rezi Castle is a ruin on a dolomite spur of Meleghegy, a 418–427 m hill on the northern rim of the Keszthely Plateau overlooking the Szántó Basin. Its surviving mass is built of irregular light grey and beige stone: a high wall with an angled, pointed top and two narrow vertical openings, a lower wall extending right, and a wooden shelter with a flat roof at the base. A red, white and green flag flies from a pole on the upper left edge.

Rezi Castle's early core was probably built by Apor of the Péc clan after 1282, when King Ladislaus IV granted the Rezi estate to Tiba of the Tomaj clan and Apor seized it by force. By 1333 it was certainly a royal possession. In 1321 Köcski Sándor recaptured it from the Kőszegi family, and Louis the Great later gave it to the Lackfi brothers, who lost it after their execution in 1397.

The castle's name survives in a local saying: "The Jews sued Rezi Castle because it did not let the sun shine on them." The gersei Pethő family held the ruin from 1433 until their male line died out in 1729, and a 1561 family council held in the castle set a garrison of twelve armed retainers.

The path to the ruins involves a hiking trail of about 5 kilometers through the mountainous terrain of Keszthely Mountain. Proper footwear is essential as the route can be muddy or slippery depending on recent weather.

The two gate towers were blown up, which is why the ruin is so fragmentary today; the remains show clearly that this was deliberate demolition. The castle was already described as ruined in a charter of 1592, after Ottoman troops raided the area and burned neighbouring Tátika in 1589.