“Now more than ever, it is time for an immediate humanitarian ceasefire,” he said in a statement after inspecting the crossing on the Egyptian side.
“It is time to silence the guns. Palestinians in Gaza, children, women, men, remain stuck in a non-stop nightmare. Communities obliterated, homes demolished, entire families and generations wiped out,” Guterres added.
Rafah is the only border crossing into the Gaza Strip that is not controlled by Israel.
Guterres earlier on Saturday met injured Palestinians at a hospital in the Egyptian Sinai city of al-Arish after they had been evacuated from the coastal strip.
“I was extremely moved by their stories, experiences and the hardships they endured,” he said.
Guterres’ visit is part of an annual trip during the Muslim holy month of Ramadan.
“This Ramadan I come to the Rafah crossing to spotlight the hardships and pain of Palestinians in Gaza,” the UN chief said.
The visit came a day after the UN Security Council failed to pass a US-backed resolution calling for a ceasefire in the Gaza war after Russia and China vetoed it.
Fears have grown that a planned Israeli military offensive in Gaza’s southernmost city of Rafah near Egypt’s border would further exacerbate the humanitarian situation in the impoverished strip.
More than 1 million Palestinians have taken refuge in Rafah after fleeing fighting elsewhere in the coastal enclave.
Guterres’ visit to the Egyptian side of Rafah was his second since the Gaza war erupted in October last year.
Israel has been pursuing its military campaign in the Gaza Strip following the unprecedented massacre by Hamas militants in Israel on October 7.
The US, Qatar and Egypt have been mediating between Hamas and Israel for weeks to broker a ceasefire and facilitate the release of hostages still held in Gaza.