"We will never recognise the legitimacy of the Israeli occupation and therefore there is no legitimacy for Israel," he added.
Meshaal was born in the West Bank but spent all his adult life in exile before arriving in Gaza on Friday for a 48-hour visit – just two weeks after an eight-day conflict between Israel and Hamas.
Hamas said it won the short conflagration, which killed 170 Palestinians and six Israelis, mostly civilians. Israel disputes this, saying it not only killed Hamas's top military commander but also destroyed much of the group's arms stockpile.
Israel tried and failed to assassinate Meshaal in 1997. It has largely ignored his visit to Gaza, though the commemorative event was mocked by Israeli officials as a celebration of "25 years of murdering Israelis by rockets and suicide bombings".