Mapam - United Workers Party (in Hebrew: מפ"ם - מפלגת פועלים מאוחדת Mifleget Poalim Meuhedet) was initially a Marxist-Zionist party. It was formed in 1948 by the merger of Hashomer Hatzair and Achdut Ha'Avoda and was active in Israeli politics until the 1990s. It was the political party of the left wing Kibbutz Artzi kibbutz movement and succeeded the earlier Hashomer Hatzair political party which had been active since the 1920s as both a party and a youth movement. Mapam was the second largest political party in Israel, second only to Mapai until the mid-1950s.
It was initially oriented towards the Soviet Union with a strong Stalinist policy until the 1953 Prague Trials shook the party's faith in the USSR. The show trials in which mostly Jewish leaders of the Communist Party of Czechoslovakia were purged, falsely implicated Mapam's envoy in Prague, Mordechai Oren. as part of a Zionist conspiracy. After the Prague Trials and, later, Nikita Khrushchev's Secret Speech at the 20th Party Congress in the Soviet Union, Mapam moved away from their more left wing positions and became a more moderate social democratic party. A number of Mapam leaders, including Moshe Sneh left the party and joined the Maki which was Israel's Communist party. At the same time Mapam suffered a right wing split with Ahdut Avoda-Po'alei Zion's departure.
Mapam remained in opposition until after the 1955 elections to the Third Knesset when it joined the Mapai led government. In 1969, Mapam joined with its former rival Mapai (which in 1968 merged with Ahdut Avoda to become the Israeli Labour Party) in an electoral alliance, the Labour Alignment with Mapam as a junior partner. Mapam left the Alignment in 1984 in protest over Shimon Peres decision to form a National Unity government with Likud. In 1992, Mapam joined with Ratz and Shinui to form the Meretz electoral coalition representing the Israeli peace camp. Mapam formerly merged with Ratz and a faction of Shinui in 1996 and ceased to exist as a separate party. (In 2004 Meretz changed its name to Yahad.)
Prominent Mapam members have included Israel Bar-Yehuda, Meir Ya'ari, Moshe Erem, Yaakov Hazan, Mordechai Bentov, Mordechai Oren, Zvi Lurie, Chaim Shur, Hanan Rubin, Yair Tsaban, and Simha Flapan.