The World Zionist Organization (Hebrew: הַהִסְתַּדְּרוּת הַצִּיּוֹנִית הָעוֹלָמִית; HaHistadrut HaTzionit Ha'Olamit), or WZO, is a non-governmental organization that promotes Zionism. It was founded as the Zionist Organization (ZO; 1897–1960) at the initiative of Theodor Herzl at the First Zionist Congress, which took place in August 1897 in Basel, Switzerland. The goals of the Zionist movement were set out in the Basel Program.

Operating under the aegis of the WZO are organizations that define themselves as Zionist, such as WIZO, Hadassah, B'nai B'rith, Maccabi, the International Sephardic Federation, the World Union of Jewish Students (WUJS), and more.

The Jewish Agency is a parallel organisation, with goals, attributes and leadership closely intertwined with those of the Zionist Organization during the years before the establishment of the State of Israel, and to varying degrees after that. Significant changes to the statutes of both organisations occurred in 1952, 1970 and 1979.