"The Syrian people feel increasingly abandoned by the world as they enter the fifth year of the war that has torn their country apart," Ban said in a statement.
The suffering continues "under the eyes of the international community, still divided and incapable of taking collective action to stop the killing and destruction," he said.
"I call upon the Security Council to take determined measures to resolve this crisis and on the way forward."
Ban's appeal for action came as more than 20 rights groups accused the Security Council of "failing Syria" despite three resolutions calling for peace efforts, access for humanitarian aid and the protection of civilians.
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A plan by UN peace envoy Staffan de Mistura for a freeze in fighting in the northern city of Aleppo appears to be making little headway, as the death toll mounts.
Last year was the deadliest yet in the war, with at least 76,000 people killed out of more than 210,000 since it began on March 15, 2011 with peaceful demonstrations, inspired by the Arab Spring in Egypt and Tunisia.
While world powers were rightfully mobilizing to defeat IS extremists, "our focus must continue to be with the Syrian people," Ban said.
He called on the international community to "unite and lend its full support" to UN efforts to forge a deal for a political transition in Syria and to bring those responsible for atrocities to justice.
"We have an obligation to the Syrian people to help ensure that serious crimes committed over the past four years do not go unpunished," he said.