Seida (Arabic: صيدا) is a Palestinian town in the Tulkarm Governorate of the State of Palestine, in the eastern West Bank, located 20 kilometers northeast of Tulkarm. According to the Palestinian Central Bureau of Statistics, Seida had a population of 3,777 in 2017.

Ceramics from the Iron Age II, Hellenistic, early and late Roman, Byzantine, early Muslim and the Middle Ages have been found here.

In 1179, during the Crusader era, it appeared as an estate, sold to the Zion Monastery in Jerusalem.

In 1265, following his victory over the Crusaders, Sultan Baibars granted Seida to his followers. The entire village was assigned to Emir Husam al-Din Itamish b. Utlis Khan.

In 1517, Seida, like all of Palestine, was incorporated into the Ottoman Empire. In the 1596 tax registers, it was part of the nahiya ("subdistrict") of Jabal Sami, part of the larger Sanjak of Nablus. It had a population of 70 households and 2 bachelors, all Muslims. The inhabitants paid a fixed tax rate of 33,3% on agricultural products, including wheat, barley, summer crops, olive trees, goats and beehives, in addition to occasional revenues and a fixed tax for people of Nablus area; a total of 12,160 akçe. All of the revenue went to a Waqf.

In 1870/1871 (1288 AH), an Ottoman census listed the village in the nahiya (sub-district) of al-Sha'rawiyya al-Sharqiyya.

In the 1882 PEF's Survey of Western Palestine (SWP), Saida is described as: "a small village, with a well on the east on the back of a long and bare ridge."

In the 1922 census of Palestine conducted by the British Mandate authorities, Saida had a population of 252 Muslims, increasing in the 1931 census to 351 Muslims, living in 75 houses.