Catherine Zeta-Jones was born Catherine Jones, in Treboeth, a working-class area of Swansea, West Glamorgan in South Wales. She is the middle of three children born to Dai Jones, a Welsh sweet factory owner, and Patricia Fair who is Irish and from a Roman Catholic family.

Her father's cousin is married to singer Bonnie Tyler, who is also from Swansea. Her uncle owns Swansea's Škoda car dealership as well as Llanelli A.F.C. football club. Her name stems from those of her grandmothers — her maternal grandmother, Katherine Fair, and her paternal grandmother, Zeta Jones.
 

After her parents won £100,000 at bingo in the 1980s, they moved to St. Andrews Drive in Mayals, an upper class area of Swansea. She attended the moderately-priced private school, Dumbarton House in Swansea where she was apparently an average student. Comedian and actor Rob Brydon also went there.

She left school early to further her acting ambitions without obtaining O levels and went on to attend The Arts Educational Schools in Chiswick for a full-time three year course in musical theatre. Zeta-Jones is married to actor Michael Douglas, with whom she has two children. She has the same birthday as her husband, although he is 25 years her senior. They were married at the Plaza Hotel in New York City on 18 November 2000. A traditional Welsh choir sang at her wedding; her wedding ring includes a Celtic motif and was bought in the Welsh town of Aberystwyth. Their son, Dylan Michael Douglas, was born 8 August 2000. Their daughter, Carys Zeta Douglas, was born April 20, 2003. While pregnant with Carys, photos were published of Zeta-Jones smoking cigarettes on a private balcony; afterwards, she became the target of anti-smoking and child health and welfare groups due to her behaviour.

Zeta-Jones has decided that her children will grow up aware of their Welsh heritage and has built a seaside home for her parents in her hometown of Swansea. She wants her children to know the Welsh language.

Her elder brother, David A. Jones (also known as Cameron Jones), is Vice President of the film company, Initial Entertainment. He was an executive producer of Gangs of New York. Her younger brother, Lyndon Jones, is her personal manager and producer for Milkwood Films. Catherine's parents recently moved from their Mayals property to a £2 million clifftop home two miles away, paid for by their daughter.