Issouf Sanogo / AFP - Getty Images, file
A young Revolutionary United Front (RUF) fighter poses near Freetown, Sierra Leone, on May 25, 1997.
Taylor is the first head of state convicted by an international court since the post-World War II Nuremberg military tribunal.
The tribunal found Taylor guilty of aiding and abetting war crimes and crimes against humanity by supporting notoriously brutal rebels in return for "blood diamonds."
Presiding Judge Richard Lussick said the warlord-turned-president provided arms, ammunition, communications equipment and planning to rebels responsible for countless atrocities in the 1991-2002 Sierra Leone civil war. Lussick called the support "sustained and significant."
Echoes of a war: A journey around Sierra Leone
Taylor stood and showed no emotion as Lussick delivered the guilty verdicts at the Special Court for Sierra Leone.
Peter Dejong / AP
Former Liberian President Charles Taylor takes notes as he waits for the start of Thursday's hearing.
Lussick scheduled a sentencing hearing for May 16 and said sentence would be passed two weeks later.
The Associated Press reported that thousands celebrated in Sierra Leone after learning that Taylor had been convicted. Countless survivors of the civil war bear emotional and physical scars from the war. Rebels hacked off the limbs of many of their victims.
Human rights advocates say the case is a reminder that even the most powerful do not enjoy impunity.
Taylor, who was president of Liberia from 1997 to 2003, was accused of backing and giving orders to Revolutionary United Front (RUF) rebels in the 11-year civil war in neighboring Sierra Leone.
'Murder and mayhem'
The prosecution alleged the RUF undermined a ceasefire agreement in 1999, prolonging the war for another three years, and that Taylor financed their war effort with the proceeds of "blood diamonds" mined illegally in Sierra Leone.
"The Taylor verdict is a watershed moment," Richard Dekker, head of the international justice program at Human Rights Watch, said before the tribunal announced its decision. "As president, Taylor is believed to have been responsible for so much murder and mayhem which unfolded in Sierra Leone. His was a shadow that loomed across the region, in the Ivory Coast, in Sierra Leone and Liberia."
Taylor denied all of the charges.
The crimes of the RUF were not in doubt. Courts have earlier convicted RUF fighters of crimes against humanity, including rape, torture and terrorism.
Civilians were mutilated during the conflict, their arms being cut off above the hand (known by fighters as "long sleeves") or above the elbow ("short sleeves").
Pregnant women shot
Trial witnesses described seeing children and pregnant women being shot, disemboweled or mutilated in a process aimed at creating terror in the civilian population.
But the challenge was to link Taylor to these crimes.
"The accused never set foot in Sierra Leone when these crimes were being committed. He never directly, physically committed these crimes," Brenda Hollis, the court's chief prosecutor, told Reuters before the verdict.
"In a domestic case, you have to prove there was a murder, we have the added level of proving linkage."
This was the reason the supermodel Naomi Campbell was summoned to give testimony to the court in 2010.
Taylor is likely to appeal, meaning the trial could easily last for another six months.
Into the jungle on the hunt for Joseph Kony
Taylor is expected to serve time in a British maximum security prison. That will contrast sharply with the comparatively luxurious life Taylor enjoys in detention in The Hague. His case was moved there because of fears that his security could not be guaranteed in Sierra Leone.
In The Hague, Taylor has been free to mix with his fellow inmates and he has maintained "cordial" relations with his old enemy Laurent Gbagbo, the former Ivory Coast leader who faces charges of crimes against humanity.
Taylor has also been known to cook and compare defense briefs with Congolese warlord Thomas Lubanga Dyilo.
As he awaited the verdict, he immersed himself in study of the Jewish faith, to which he converted before arriving in The Hague. He has regular visits from a rabbi and does not receive his lawyers on the Sabbath.
By msnbc.com staff and news services
Updated at 8:01 a.m. ET:
The Associated Press, Reuters and msnbc.com staff contributed to this report.