The star is accused of racketeering, sexual abuse and bribery; charges which he has repeatedly denied.
Some of the allegations made against the singer - whose full name is Robert Sylvester Kelly - date back more than 20 years.
If he is convicted on all counts he could be sentenced to several decades in prison.
Opening statements were delivered to a jury of seven men and five women, who will decide the 54-year-old singer's fate.
Mr Kelly faces charges that he was the ringleader of a two-decade scheme where he recruited women and underage girls for sex.