As reported by BBC:
Guillaume, who became one of the most prominent black actors on US TV, was best known for his role as the surly butler in the sitcoms Soap and Benson.
He died at his home in Los Angeles on Tuesday, his wife Donna Brown said.
It is not known how long the actor, who was awarded two prestigious Emmy Awards, had been battling cancer.
Guillaume first played the cantankerous but loveable butler Benson DuBois in the popular series Soap, which debuted in 1977.
His character became such a hit among his US audience that it led to the spin-off series Benson, which ran for seven seasons from 1979 to 1986.
Guillaume won an Emmy for outstanding supporting actor in the comedy series Soap in 1979 and was the first black actor to win outstanding lead actor for Benson in 1985.
His distinctive voice earned him the title role in a 1990 production of Phantom of the Opera in Los Angeles.
He is also known as the voice of the mandrill Rafiki in the 1994 Disney animated film The Lion King.
In 1999, Guillaume suffered a minor stroke at the age of 71 but was able to return to work following several weeks in hospital.
Born Robert Peter Williams in 1927, he changed his name to Guillaume to make it more distinctive.
He is survived by his second wife, a son and three daughters.