Gazans cheered and waved Palestinian flags as the convoy finally entered the territory through the Rafah border crossing on Monday, after being stranded on the Egyptian side of the border for two days.
"The group was stopped at the border for various reasons, there were various negotiations going on over what would be let through the border; how many people, how much humanitarian aid," Al Jazeera's Todd Baer, reporting from the Rafah crossing, said.
"After an 8,000km journey, nearly one month on the road and a day and a half on the Egyptitan side of the Rafah border, the Lifeline for Gaxa convoy finally made it into the Gaza Strip. It was a remarkable scene."
The passage of the convoy through Egypt had been controversial.
The convoy was pelted with stones and vandalised in the Egyptian town of El-Arish, 45km south of the Rafah border crossing, before being cleared to enter Gaza.
'Overwhelmed with happiness'
As he entered Gaza, Galloway said he was "overwhelmed with happiness".
"I have entered Palestine many times but the most emotional of these is after the 22-day genocidal aggression against the Palestinian people," he said.
Galloway said that he planned to meet "the heroes of Palestine's resistance, the government of Palestine, the people of Palestine".
The convoy comprising 110 vehicles has brought aid supplies valued at $1.4m.
Israel's Gaza offensive, which it said was aimed at stopping rocket and mortar attacks by Palestinian fighters, devastated the Gaza Strip. More than 1,300 Palestinians were killed and thousands of homes were destroyed in the assault which ended in January.
Israel and Egypt have sealed Gaza off from all but limited humanitarian aid since Hamas seized full control of the territory in June 2007 after pushing out forces loyal to Mahmoud Abbas, the West Bank-based Palestinian president.