Barak was born in a kibbutz that had been founded by his father, an emigrant from Lithuania, in 1932. Barak was drafted into the Israel Defense Forces in 1959, thus beginning a distinguished military career (he changed his name at this time). He was a commander in battles in the Six-Day War (1967) and the Yom Kippur War (1973) but became especially known as the leader of special forces units that conducted commando raids. These included a group of soldiers (with Benjamin Netanyahu (Netanyahu, Benjamin) among them) who stormed an airliner hijacked by Palestinian guerrillas at Lod International Airport near Tel Aviv in 1972, freeing all the hostages. Barak served as head of military intelligence, and in 1991 he became chief of General Staff. In 1994 he participated in the negotiations that resulted in a peace accord with Jordan. When he retired in 1995 as a lieutenant general, the army's highest rank, he was the most decorated soldier in Israeli history.

Barak had received a B.Sc. degree in physics and mathematics from Hebrew University of Jerusalem (1968) and an M.Sc. degree in economic engineering systems from Stanford University in California (1978). He turned his attention to politics in the mid-1990s. Under Labour governments he was minister of the interior in 1995 and minister of foreign affairs in 1995–96. He was elected to the Knesset (Israeli parliament) in May 1996. In June 1997 he became head of the Labour Party (Israel Labour Party) and two years later ran for prime minister under the coalition One Israel, which included Labour as well as the Gesher Party and Meimad, the latter a spin-off of the National Religious Party. Barak emphasized economic and other domestic issues, including education and health services, as well as relations with the Palestinians and with Syria and Lebanon. The withdrawal of minor candidates late in the campaign allowed a face-off between incumbent Netanyahu, of the ruling Likud party, and Barak. On May 17, 1999, Barak won an easy victory with slightly more than 56 percent of the popular vote. At the same time, smaller parties increased their seats in the Knesset. The election results were seen as a turning away from the hard-line policies, particularly in relations with the Palestinians, pursued by Netanyahu.

As prime minister, Barak pledged to establish peace in the Middle East, and in September 1999 he reactivated peace talks with Palestinian leader Yāsir ʿArafāt (Arafāt, Yāsirʿ). The two men signed a deal that called for the creation of a final peace accord by September 2000 as well as the transfer of more Israeli-occupied territory in the West Bank to Palestinian control. In December 1999, Barak resumed peace talks with Syria after more than three years of deadlock, and he also ended Israeli's 17-year occupation of southern Lebanon.

Beginning in the summer of 2000, however, Barak faced a series of crises. In July his coalition collapsed after three parties quit, leaving him with a minority government. Later that month he narrowly won a vote of confidence in the Knesset. In September violence erupted in the West Bank and Gaza, seriously threatening the peace talks. Barak met with ʿArafāt, but the resulting cease-fire agreement was all but ignored. As fighting continued, Barak announced a time-out from peacemaking. The move was thought to appease the growing opposition to Barak's government, especially that led by Ariel Sharon (Sharon, Ariel), the Likud party leader. In December 2000 Barak resigned as prime minister, and a new election was slated for February 2001. Barak ran for reelection but was criticized by many Israelis for his inability to halt the violence and for allegedly making too many concessions during the peace talks. At the polls, they overwhelming cast their ballots for Sharon. After receiving only 37 percent of the vote, Barak announced his resignation both as Labour leader and as a member of the Knesset. In 2007 Barak staged a political comeback as he was reelected leader of the Labour Party. Soon after, he became the country's defense minister.