Congolese warlord Thomas Lubanga has been sentenced to 14 years in jail for recruiting and using child soldiers in his rebel army in 2002 and 2003.
He was convicted by the International Criminal Court (ICC) in March - the first conviction since the court was set up 10 years ago.
Lubanga had protested his innocence and said he had not supported the use of child soldiers.
But in a unanimous decision, the judges said Lubanga was responsible.
Lubanga showed no emotion as the presiding judge read out the sentence.
Judge Adrian Fulford told the court in The Hague that, taking into account the time Lubanga has already spent in jail, he will effectively spend eight more years behind bars.
Campaign group Human Rights Watch says more than 60,000 people were killed in the conflict between Hema and Lendu ethnic groups in Ituri, in north-eastern DR Congo.
In June, ICC chief prosecutor Luis Moreno-Ocampo said he was asking for a "severe sentence" of 30 years.
He said the prosecution was requesting a sentence "in the name of each child recruited, in the name of the Ituri region".
The conviction of Lubanga is linked to current unrest in DR Congo.
Rebel forces are advancing towards the country's main eastern city of Goma.
They are headed by Gen Bosco Ntaganda, who is also wanted for war crimes by the ICC.