list family officesstanderlampeThe BBC's Will Ross in Juba says people flocked to the event on a baking hot day - some of them climbing trees to get a view.
The Speaker of the South Sudan Legislative Assembly, James Wani Igga, read out the Proclamation of the Independence.
Crowds then cheered as Sudan's national flag was lowered and the new flag of South Sudan was raised as trumpets played the new national anthem.
Afterwards the master of ceremonies told the crowd that President Kiir has decided not to hand over the flag of the Republic of Sudan