The global body says its former chief prosecutor for war crimes in Yugoslavia and Rwanda, Richard Goldstone, will head the probe ordered by the Human Rights Council in January.
According to a Palestinian rights group, 1,417 people including 926 civilians were killed in the fighting. Thirteen Israelis also died. Israel has refused cooperation with previous council probes, calling them biased.
"It is in the interest of all Palestinians and Israelis that the allegations of war crimes and serious human rights violations related to the recent conflict on all sides be investigated," Goldstone said in a statement.
"I am confident that the mission will be in a position to assess in an independent and impartial manner all human rights and humanitarian law violations committed in the context of the (Gaza) conflict," the president of the Human Rights Council, Nigerian ambassador Martin Uhomoibhi, said in a statement.
Goldstone will be accompanied by British human rights professor Christine Chinkin, Pakistani lawyer Hina Jilani and retired Irish Army colonel Desmond Travers.
Reuters and The Associated Press contributed to this report