Mashaal has led Hamas since 1996, helping to build the Iranian-backed movement into a potent force. Under his leadership, Hamas carried out numerous suicide bombings and other attacks on buses, cafes and other public places that killed hundreds of Israelis during a Palestinian uprising a decade ago. The group has been branded a terrorist organization by Israel, the U.S. and the European Union.
He also survived an Israeli assassination attack in Jordan in 1997. Until recently, he was based in Syria but after civil war broke out there relocated to Qatar.
Hamas overtook Gaza from forces loyal to Palestinian President Mahmoud Abbas' Fatah party in 2007. It has yet to reconcile with Fatah, which rules the West Bank.
The announcement of Mashaal's Gaza visit comes after the United Nations voted overwhelmingly Thursday to accept a Palestinian state in the West Bank, the Gaza Strip and east Jerusalem as a non-member observer state.
Abbas has said he hopes the U.N. bid with help restart frozen peace talks with Israel over a future Palestinian state. But he refuses to negotiate so long as Israeli settlement construction continues. Israeli Prime Minister Benjamin Netanyahu says peace talks must resume immediately but without preconditions.
The day after the vote, Israel responded to U.N. recognition of a Palestinian state, deciding to build 3,000 more homes for Jews in the West Bank where the Palestinians want to build their future state.
Hamas refuses to recognize Israel and is still committed to its destruction. It did not interfere with the U.N. bid for statehood, and its supporters joined some of the celebrations that followed the announcement.
Israel and Hamas are observing a truce that ended eight days of cross-border fighting in November. It was the bloodiest fighting between Israel and Gaza militant groups Islamic Jihad and Hamas in four years. Israel says it launched the offensive to curb daily Palestinian rocket attacks from Gaza at Israeli cities that had intensified in the months before. More than 160 Palestinians and six Israelis were killed in the fighting.
Palestinian militants led by Hamas showered Israel with more than 1,500 rockets throughout the campaign despite Israeli airstrikes. The Palestinian militants managed to launch longer-range weapons that exploded deep into the Israeli heartland near Jerusalem and Tel Aviv.
Hamas feels they came out on top from the fighting because they succeeded in holding their own while winning concessions from Israel as part of the ceasefire agreement.