Streamers and balloons dotted the sky above Gaza City as Palestinians gathered to celebrate 20 years since the founding of Hamas.
At least 300,000 people turned out and the crowd became a sea of green as Hamas banners were hoisted.
Hamas Prime Minister Ismail Haniya addressed the rally with a huge poster of the group's founder, Sheikh Ahmed Yassin, behind him.
Israeli flags were burnt as the group underpinned its message that it does not recognise Israel's right to exist as a state.
Hamas, which has on occasion fought both Israel and its mainstream Palestinian rivals Fatah, posted guards to cover the demonstration.
As part of the celebrations, horsemen rode around with the Hamas banner.
The rally is said to be the biggest show of Hamas strength since the group seized control of Gaza in June.