Mabel King (born Donnie Mabel Elizabeth Washington, December 25, 1932 - November 9, 1999) was an American actress. She was born in Charleston, South Carolina and was raised in Harlem.

King did not start acting until her late thirties. Even though she started acting fairly late in life, she first earned success playing the Wicked Witch of the West in the Broadway and movie versions of The Wiz.

However, she is most known for her role as Mabel Thomas on the sitcom What's Happening!!, a role she played from 1976 to 1978.

She popularized the catch phrase "This is true", which she said often to her children when she tried to prove a point to them.

After the show ended, her most notable movie role was in the Steve Martin movie The Jerk, which she reprised for a TV movie sequel.

In the 1990s, she battled diabetes, and eventually lost both of her legs and an arm to the disease. In 1999, she succumbed to complications from diabetes, aged 66.