"No one is allowed to give up any part of Palestine," he said during a meeting with Gaza prime minister Ismail Haniya and members of the government.
Egyptian-born Qaradawi, who is a citizen of Qatar and close to the Muslim Brotherhood, was heading of a delegation of 50 clerics from 14 countries.
"Palestine was never Jewish," he said. "Palestine is Arab and Muslim and will remain Arab and Muslim, and Islam will prevail."
Haniya, who handed Qaradawi a Palestinian passport, reaffirmed that his Islamist movement would "never give up or recognise Israel."
"We will not give up our rights, we will never give up an inch of Palestine and won't allow anyone to cede a grain of Palestinian land," he said.
The 86-year-old Qaradawi, who last visited the Gaza in 1958, arrived on Wednesday night for a three-day visit he said was to "support its people and participate in lifting the (Israeli) blockade against them."
Last month, he boycotted an inter-faith forum in Doha because Jews were invited to the conference.
Qaradawi, head of the Association of Muslim Scholars, is a controversial religious figure in the West and has millions of supporters -- mainly from the Muslim Brotherhood.
He hosts a popular show on Al-Jazeera television and backed the Arab Spring uprisings in Tunisia, Egypt, Libya and Syria.
Qaradawi was refused a French visa last year on the grounds of being anti-Jewish. He was banned from entering Britain in 2008 and has been banned from the United States since 1999.