Jamma'in (Arabic: جمّاعين) is a Palestinian town in the Nablus Governorate of the State of Palestine, in the northern West Bank, located 16 kilometers (9.9 mi) southwest of Nablus, 6 kilometers (3.7 mi) northwest of Salfit and 40 kilometers (25 mi) north of Ramallah. According to the Palestinian Central Bureau of Statistics, the town had a population of 7,436 in 2017.

Jamma’in is located 11.26 km south of Nablus. It is bordered by 'Einabus and Huwwara to the east, Yasuf, Iskaka and Marda to the south, Zeita Jamma'in to the west, 'Asira al Qibliya and 'Urif to the north.

Jamma'in is situated on a high hill on the ancient site. Carved stones have been reused in village houses, walls, fencing and agricultural terraces. Rock-cut cisterns have also been found. 400 meters north-west are tombs carved into rock which contains one loculi and caves (called I-Qubay'ah).

Sherds from the Iron Age I, IAII, Persian, Hellenistic, Roman and Byzantine eras have also been found here.

A village in the Crusader era (1123 CE) named "Gemmail", has been identified with Jamma'in. It was referred to as "Jamma'il" in medieval Arabic sources. The village was home to the Bani Qudama clan, who moved to Damascus in 1156, during Crusader rule in Palestine. Their leader, and the khatib (Muslim preacher) of the village, Ahmad ibn Qudama (father of Ibn Qudamah and grandfather of Diya al-Din), left Jamma'in due to fears of persecution by King Baldwin, who intended to punish Ibn Qudamah for preaching against Crusader rule. The hilly and uninhabited area of Damascus the Banu Qudamah settled became the al-Salihiyah suburb, which was named either after the family, who were known as "the pious ones" (as-salihiyyin) or after the Abi Salih Mosque, which the family was associated with. Throughout the 11th and 12th centuries, Jamma'in was a center for Hanbali activity. The medieval Syrian geographer Yaqut (1179–1229) described the site as "A well in the hill of Nabulus, in the Filastin Province. It lies a day's journey distant from Jerusalem, and belongs to that city." Diya al-Din (1173-1245) refers to the presence of Muslims in Jamma'in during his lifetime, and he also noted that the village had a mosque.

Crusader/Ayyubid and Mamluk sherds have also been found here.

Jamma'in was incorporated into the Ottoman Empire in 1517 with all of Palestine, and in 1596 it appeared in the tax registers as being in the nahiya of Jabal Qubal, part of Nablus Sanjak. It had an entirely Muslim population of eighteen households and five bachelors. The inhabitants of the village paid a fixed tax rate of 33.3% on wheat, barley, summer crops, olive trees, goats and/or beehives, and a press for grapes or olives; a total of 7,800 akçe.

In the 17th century, the Qasim family ruled Jamma'in and twenty nearby villages, including Awarta, Beit Wazan, Haris and Zeita. Jamma'in was the seat of the namesake Jamma'in subdistrict of the District of Nablus.Situated between Dayr Ghassāna in the south and the present Route 5 in the north, and between Majdal Yābā in the west and Jammā‘īn, Mardā and Kifl Ḥāris in the east, this area served, according to historian Roy Marom, "as a buffer zone between the political-economic-social units of the Jerusalem and the Nablus regions. On the political level, it suffered from instability due to the migration of the Bedouin tribes and the constant competition among local clans for the right to collect taxes on behalf of the Ottoman authorities.”