Viola Davis has said she ''thanks God'' for her mother.

The 51-year-old actress took to Instagram on Thursday (04.05.17) to share a sweet snap of her mother Mary in honour of her 74th birthday, praising the woman as being her ''rock'' and her ''joy''.

Posting a picture of her mother sat at a table with her birthday cake, the 'Fences' actress wrote: ''This woman came into the world May 4th,1943. Of course, I am convinced that the universe shifted that day. I am also convinced that anyone, who has had the honor of meeting her, feels the same way. Happy 74 years of life mama. My love. My joy. My frustration. My rock. Love, love you with every fiber of my being. I thank God for you! HAPPY BIRTHDAY!!! (sic)''

Viola - who suffered extreme poverty as a child - is now a mother herself to five-year-old daughter Genesis, whom she has with her husband Julius Tennon, and previously spoke about how her biggest fear is that her daughter will grow up to be ''entitled'' and not appreciate what she has.

When asked how she balances wanting Genesis to have more than she did as a child, and wanting her to appreciate what she has, Viola said: ''You just listed my number one fear, which is entitlement. I never had a house; I do shop at Target, I buy all her clothes at Target or H&M. And maybe, if I'm feeling really good, Nordstrom Rack.''

And the 'How To Get Away With Murder' star said her husband and actor Julius, 63, helps her keep Genesis grounded as he always ''holds her accountable'' for the things she does.

Viola - who has been married to Julius since 2003 - said: ''Julius is really tough. He has two beautiful children and seven grandkids. I came into a relationship where he already had children and grandchildren and raised his kids on his own, so he's tough -- he toes the line, but in a very loving way.

''He holds her accountable. Me, not so much -- I'm the softie. Really, entitlement. Listen, there are poor kids who are entitled. So I pray.''