Michael Adebolajo, 29, and Michael Adebowale, 22, crashed into Fusilier Rigby in a car and then hacked him to death with a meat cleaver and knives.
The brutal attack took place in front of horrified onlookers near Woolwich Barracks in south east London.
A jury took little more than an hour to find the pair guilty at the Old Bailey courthouse on December 19, 2013, Thursday.
However, Adebolajo and Adebowale were cleared of the attempted murder of a police officer.
The relatives of murdered Lee Rigby broke down in tears as the verdicts were given.
Rebecca Rigby, widow of British soldier Lee Rigby, reacts during a statement to the media at the Old Bailey.