The General Assembly has admitted South Sudan as the 193rd member of the United Nations.
The assembly vote, by acclamation, followed the African country's achievement of independence on July 9, breaking away from Sudan.
South Sudan achieved independence after its people voted for secession from the rest of the country in a January referendum, under the terms of a 2005 peace deal that ended a 20-year war between north and south Sudan.
Sudan became independent in 1956 but was long plagued by conflict between its mainly Muslim Arabic-speaking north and its south, where many are Christian or follow traditional beliefs.
The last country to achieve UN membership was Montenegro in 2006 but veto-holding China and Russia have blocked Taiwan and Kosovo, respectively, from joining the world body.
Some 7,000 UN blue helmets will continue to serve in South Sudan.
compiled from agency reports