Orestiada (Greek: Ορεστιάδα, romanized: Orestiáda, formerly Ancient Greek: Νέα Ορεστιάς, romanized: Néa Orestiás), is the northeasternmost, northernmost and newest city of Greece and the second largest of the Evros regional unit of Thrace. It was founded in 1923 by Greek refugees from Edirne, after the population exchange between Greece and Turkey. It has a population of about 20,000.

In ancient times, there was Orestias, a small settlement on this site which legends claim was founded by Orestes, the son of Agamemnon and Clytemnestra.

Following the Greco-Turkish War (1919–1922) and the Armistice of Mudanya (October 1922), the Western Forces surrendered Eastern Thrace to Turkey and the Greek army was ordered to withdraw within 15 days to positions east of Evros. As a result, Adrianople (renamed Edirne) which is located to the east of Evros, became Turkish, but Karagatch (Karaağaç), located to the west of Evros, remained in Greece. As Eastern Thrace was evacuated by its Greek population, several residents of Edirne fled to its neighboring suburb, Karagatch, on the other bank of the river (the west and still Greek), hoping that something would change and they could go back to their homes more easily. However at the Lausanne conference, Karagatch was transferred to Turkish control.

The 17,000 Greek inhabitants of the Karagatch Triangle learned of this concession on 27 May 1923. The abandonment of the old Orestiada began in July 1923, as the population moved beyond the Evros River, the new border. On 4 June 1923, a committee, which had only been formed the day before at a joint meeting of the inhabitants of old Orestiada, traveled 17 kilometers south, to the uninhabited rural site of Kum-Tsiflik (Sandy Estate), to view the possible new settlement. On 12 August 1923, the new city called New Orestiada was inaugurated to remind the old Orestiada, Karagatch. The inauguration of the new city took place in August 1923 by the Metropolitan of Adrianople Polycarpos, with Spyros Dassios also in attendance.

Orestiada has a medical center, an orchestra, and a choir as well as a sugar factory, outside the city which processes locally grown sugar beets. Asparagus, potatoes, tobacco, watermelons, and corn are also grown. As well, a cattle breeding fund gives commercial impetus to the city and the whole area which is in such an economically strategic location in Europe.

It is also the site of the Fylakio detention center for refugees seeking asylum in Greece. In November 2010, the European Union sent Frontex forces to Orestiada to help Greek police patrol the local section of the border with Turkey. Some 31,400 people crossed just that portion of the border in the first nine months of 2010.

Orestiada lies in the plain of the river Evros, at 40 metres above sea level. Orestiada is only 6 km west of the banks of the Evros, which forms a natural border between Greece and Turkey. Orestiada is located 17 km north of Didymoteicho, 19 km south of Edirne, 28 km southeast of the Greek-Turkish-Bulgarian tripoint, 40 km southeast of Svilengrad, 91 km northeast of Alexandroupoli, and 212 km west of Istanbul.

The Greek National Road 51/E85 passes 1 km to the west of Orestiada.