The eldest daughter of the late John Patrick Fox and Carole Ann Wilken, Samantha Karen Fox comes from a family of market traders in the East End of London. She has a sister, Vanessa, who is six years younger, and a half-sister, Frederica, from her father's second marriage.

She attended St Thomas More RC School, Haringey, and took a keen interest in the theatre from an early age. She first appeared on a theatre stage at the age of three, and was enrolled in the Anna Scher Theatre School from the age of 5. Her first television appearance came in 1976, at the age of 10, in a BBC play entitled No Way Out. Following on from this, she started at the Judi Dench Mountview Theatre School, near her home in Haringey, at the age of 11.

Interested in music from an early age, she formed her first band, with Richard Smart on guitar, Edward Gallagher on triangle and Bob Day on tambourine, at the age of 14. Her first record deal came a year later, with Lamborghini Records. However, both her theatre and music careers went on hold when her modelling career took off.

In early 1983, Carole Fox photographed her teenage daughter wearing lingerie and submitted several pictures to The Sunday People newspaper's "Face and Shape of 1983" amateur modeling contest. Judged joint runner-up in the contest, Fox had her pictures published, and was soon after invited for a test shoot for The Sun newspaper's Page Three feature. Her parents gave their consent for their daughter to pose topless, and on Tuesday, 22 February 1983, Fox's first Page Three photograph was published under the headline "Sam, 16, Quits A-Levels for Ooh-Levels".

Fox's Cockney background, bubbly-blonde looks, winning smile, and 36D breasts made her an enormously popular Page Three model. After famously insuring her breasts for a quarter of a million pounds sterling, she won The Sun's Page Three Girl of the Year award for three consecutive years between 1984 and 1986. She also posed nude for several British men's magazines and was a UK Penthouse Pet, but very few full-frontal shots were ever published.

Fox retired from Page Three modelling in 1986, at the age of 20, by which time she had arguably become Britain's premiere sex symbol of the era. In 1995, aged 29, she made a one-off appearance in The Sun to promote Page Three's 25th anniversary week. After receiving an overwhelmingly positive reader response, she appeared in the slot every day during the anniversary week, with Friday's final topless picture given away as an A3-sized poster. In 1996, aged 30, she appeared in the October issue of Playboy magazine.

Fox's father Patrick, a former carpenter, managed her career until 1991, when Fox hired accountants to trace over £1 million that she believed he had embezzled from her accounts. She then sued her father, who by then had divorced and remarried, and in May 1995 she was awarded a £363,000 court settlement. Patrick Fox died in 2000, at which time he and Fox had not spoken for almost a decade.

Samantha Fox was, in a online vote held by the British Newspaper the Daily Star, voted by its readers, as 'The best page 3 pin up ever' in September 2008. As a result of the poll win, she appeared topless for the first time in 12 years in the Daily Star although on page 5, not page 3.

In the late-1980s, Fox began a successful singing career, producing three albums in three years (1986–1988), and working with notable music producers such as Stock Aitken Waterman and Full Force.

Samantha Fox released her debut single, "Touch Me (I Want Your Body)", when she was 19 years old in March 1986. The single made the Top 10 on both sides of the Atlantic (#3 in the UK; #4 in the US). It also topped the charts in many countries, including Canada, South Africa and Australia. Her debut live performance came at Peter Stringfellow's club Hippodrome.