The Zionist movement acquired British and League of Nations sponsorship after World War I, resulting in the creation of the British Mandate of Palestine, which specifically called for "placing the country under such political, administrative and economic conditions as will secure the establishment of the Jewish national home." After an often tumultuous Mandate period, and after the Holocaust had destroyed Jewish society in Europe, the Zionist movement culminated in the establishment of the State of Israel in 1948.

Since the founding of the State of Israel, the term Zionism has come generally to mean support for Israel. However, a variety of different, and sometimes competing, ideologies that support Israel fit under the general category of Zionism, such as Religious Zionism, Revisionist Zionism, and Labour Zionism. Thus, the term is also sometimes used to refer specifically to the programs of these ideologies, such as efforts to encourage Jewish immigration to Israel.

The term Zionism is also sometimes used retroactively to describe the millennia-old Biblical connection between the Jewish people and the Land of Israel, which existed long before the birth of the modern Zionist movement. The label Zionist is also used improperly as a euphemism for Jews in general by those wishing to white-wash anti-Semitism (as in the Polish anti-Zionist campaign).

In addition to Jewish Zionism, there was always a small number of Christian Zionists that existed from the early days of the Zionist movement. According to Prof. Charles Merkley from Carleton University, Christian Zionism strengthened significantly after the 1967 Six Day War, and many Dispensationalist Christians, especially in the United States, now strongly support Jewish Zionism. Today, Christian Zionists greatly outnumber Jewish Zionists.

The word "Zionism" is derived from the word "Zion", one of the names of Jerusalem, as mentioned in the Bible. It was coined as a term for Jewish nationalism by Austrian Jewish publisher Nathan Birnbaum in his journal Self Emancipation in 1890.A key event triggering the modern Zionist movement was the Dreyfus Affair, which erupted in France in 1894. Among those who witnessed the Affair was an Austrian-Jewish journalist, Theodor Herzl, who published his pamphlet Der Judenstaat ("The Jewish State") in 1896. Prior to the Affair, Herzl had been anti-Zionist, afterwards he became ardently pro-Zionist.

In 1897 Herzl organised the First Zionist Congress in Basel, Switzerland, which founded the World Zionist Organisation (WZO) and elected Herzl as its first President.

The Zionist leaders always saw Britain as a key potential ally in the struggle for a Jewish homeland. Not only was Britain the world's greatest imperial power; it was also a country where Jews lived among them influential political and cultural leaders, such as Benjamin Disraeli and Walter, Lord Rothschild.

This hope was realised in 1917, when the British Foreign Secretary, Arthur Balfour, made his famous Declaration in favour of "the establishment in Palestine of a national home for the Jewish people". Balfour was motivated partly by philo-Semitic sentiment, partly by a desire to weaken the Ottoman Empire (an ally of Germany during the First World War), and partly by a desire to strengthen support for the Allied cause in the United States, home to the world's most influental Jewish community.

Support for the Zionist movement was not initially a mainstream position in the world Jewish community, and it was actively opposed by many Jewish organizations. While traditional Jewish belief held that Eretz Yisrael (the Land of Israel) was given to the ancient Israelites by God, and that therefore the right of the Jews to that land was permanent and inalienable, most Orthodox groups held that the Messiah must appear before Israel could return to Jewish control, and Reform Judaism explicitly rejected Zionism. Still, return to the Land of Israel had remained a recurring theme among generations of diaspora Jews, particularly in Passover and Yom Kippur prayers which traditionally concluded with, "Next year in Jerusalem."