Meshaal, in exile for 45 years before visiting Gaza this week, spoke on the 25th anniversary of the founding of Hamas.
Reconciliation was a key theme. He called for a singular Palestinian leadership led by the PLO, but he was unbending in his support of Hamas' goals.
"Palestine is ours from the river to the sea, from the north to the south," Meshaal said. "It is our right, our homeland. We will not give up any inch or any part of it."
The Hamas leader's provocative speech came two weeks after a bloody fight with Israel that left the group energized and emboldened.
The goal of Hamas is an Islamic fundamentalist Palestinian state. Its manifesto advocates the destruction of the state of Israel and calls for the raising of "the banner of Allah over every inch of Palestine."
Israel, the United States and other Western countries label Hamas a terrorist organization. The United States also has listed Meshaal as a terrorist since 2003.
Palestine is an Arab and Islamic land, Meshaal said, and "it is for us, not for others."
Meshaal spoke to a packed crowd that waved green Hamas flags, but the leader spoke of wider unity under the Palestine Liberation Organization, chaired by Mahmoud Abbas.
Abbas' Fatah movement and Hamas have often been at odds politically and militarily following Hamas' electoral victories in Gaza.
The Palestinians need "one government, one authority, one legislative council," Meshaal said.
Abbas, who is the president of the Palestinian Authority, has sought to advance a Palestinian state through diplomatic means, most recently by securing an upgrade at the United Nations for his people to nonmember observer state.
"It is a small step, but a good one," Meshaal said.
But it was clear Saturday that the Hamas leader's preferred strategy remains armed conflict.
"The jihad and military resistance is the road and is the real and correct way to liberate Palestine," he said.
Political, diplomatic and legal struggles are necessary, he said, but they all follow military efforts.
Meshaal, who has led Hamas from exile since 2004, was making his first visit to Gaza and his first to the Palestinian territories in 45 years. He left the Palestinian West Bank in 1967 at the age of 11 after Israel moved into the territory during the Six-Day War. Israel, under Prime Minister Benjamin Netanyahu, attempted to assassinate him in 1997.
If there existed a peaceful path to a Palestinian state, Hamas would follow that path, but it is not an option, Meshaal said.
He described the recent eight-day conflict with Israel, where rocket attacks were met with Israeli airstrikes and which ended with a cease-fire, as a victory for Hamas in Gaza.
Gaza stood fast and surprised the Israelis with their attacks, he said.
"Bless those hands who fired missiles upon Tel Aviv," he said. "This is how victories are made."
Meshaal also was unequivocal that while he seeks Palestinian unity, Hamas would not shift its position on not recognizing Israel.
A Palestinian state should never have to recognize what Hamas considers to be an occupying power, he said.