Rekha was born in Madras on 10 October 1954 to Tamil actor Gemini Ganesan and Telugu actress Pushpavalli. Her father did not acknowledge his paternity during her childhood.

Rekha has a sister, one half-brother and five half-sisters. It was in early 1970s, when she was looking for a footing in Bollywood, that she revealed her origins. Later, at the peak of her career, Rekha told a magazine interviewer that her father's neglect still rankled and that she had ignored his efforts at reconciliation.

Rekha attended Sacred Heart Convent for Girls in Yercaud, Tamil Nadu. At the age of 13, she quit school to start a career in acting. She did not have any personal aspirations in this direction, but the troubled financial state of her family compelled her to do so.

She considers Telugu to be her mother tongue. She has stated that she thinks in English.

1970s

Rekha appeared as a child (credited as Baby Bhanurekha) in the Telugu film Rangula Ratnam (1966). Rekha made her debut as heroine in the successful Kannada film Operation Jackpot Nalli C.I.D 999 with Rajkumar in 1969. In that same year, she starred in her first Hindi film, Anjana Safar. She later claimed that she was tricked into a kissing scene with the leading actor Biswajit for the overseas market, and the kiss made it to the Asian edition of Life magazine. The film ran into censorship problems, and would not be released until almost a decade later in 1979 (retitled as Do Shikaari).

She had no interest in acting and was basically forced to work to sustain her family financially, this was a difficult period in her life. Still a teenager, acclimatising herself to her new surroundings was an uneasy process. Coming from the South, she did not speak Hindi and struggled to communicate with co-workers, and was constantly missing her mother, who was critically ill. Moreover, she was required to follow a strict diet. Recalling this phase, Rekha was later quoted as saying (Reacting to it, many years later, she said, "I'm healed, I am not bitter anymore, I don't think I ever was."),

She had two films released in 1970: the Telugu film Amma Kosam and the Hindi film Sawan Bhadon, which was considered her acting debut in Bollywood. She had to learn Hindi, as that was not her naturally spoken language. Sawan Bhadon became a hit, and Rekha – a star overnight. Despite the success of the film, she was often scorned for her looks. She subsequently got several offers but nothing of substance, as her roles were mostly just of a glamour girl. She appeared in several commercially successful films at the time, including Raampur Ka Lakshman (1972), Kahani Kismat Ki (1973), and Pran Jaye Par Vachan Na Jaye (1974), yet she was not regarded for her acting abilities and—according to Tejaswini Ganti—"the industry was surprised by her success as her dark complexion, plump figure, and garish clothing contradicted the norms of beauty prevalent in the film industry and in society." Rekha recalls that the way she was perceived at that time motivated her to change her appearance and improve her choice of roles: "I was called the ‘Ugly Duckling’ of Hindi films because of my dark complexion and South Indian features. I used to feel deeply hurt when people compared me with the leading heroines of the time and said I was no match for them. I was determined to make it big on sheer merit."

This period marked the beginning of Rekha's physical transformation. She started paying attention to her make-up, dress sense, and worked to improve her acting technique and perfect her Hindi-language skills. To lose weight, she followed a nutritious diet, led a regular, disciplined life, and practised yoga, later recording albums to promote physical fitness. According to Khalid Mohamed, "The audience was floored when there was a swift change in her screen personality, as well as her style of acting." She began choosing her film roles with more care; her first performance-oriented role came in 1976 when she played Amitabh Bachchan's ambitious and greedy wife in Do Anjaane. An adaptation of Nihar Ranjan Gupta's Bengali novel Ratrir Yatri, the film was directed by Dulal Guha and became a reasonable success with audiences and critics.

Her most significant turning point, however, came in 1978, with her portrayal of a rape victim in the movie Ghar. She played the role of Aarti, a newly married woman who gets gravely traumatised after being gang-raped. The film follows her character's struggle and recuperation with the help of her loving husband, played by Vinod Mehra. The film was considered her first notable milestone, and her performance was applauded by both critics and audiences. Dinesh Raheja from Rediff, in an article discussing her career, remarked, "Ghar heralded the arrival of a mature Rekha. Her archetypal jubilance was replaced by her very realistic portrayal..." She received her first nomination for Best Actress at the Filmfare Awards.

In that same year, she attained fame with Muqaddar Ka Sikandar, in which she co-starred once again with Amitabh Bachchan. The movie was the biggest hit of that year, as well as one of the biggest hits of the decade, and Rekha was set as one of the most successful actresses of these times. The film opened to a positive critical reception, and Rekha's performance as a courtesan named Zohra, noted for a "smouldering intensity", earned her a Best Supporting Actress nomination at the Filmfare.

1980s

In 1980, Rekha appeared in the comedy Khubsoorat, directed by Hrishikesh Mukherjee, with whom she had developed a strong father-daughter bond during their previous collaborations. In a role written specially for her, she played Manju Dayal, a young vivacious woman who visits her recently married sister at her in-law's house and tries to bring joy to the wide family, much to the displeasure of the matriarch of the household. Rekha said she easily identified with the bubbly nature of her character, calling it "quite a bit me". Khubsoorat was a success and Rekha was appreciated for her comic timing. It won the Filmfare Award for Best Film and Rekha won her first Best Actress award. The Tribune described the film as "a lively comedy," noting that "Rekha's spunky performance gives the film its natural zing." Film World magazine reported in that same year, "Rekha's done it. Smoothly, successfully. From a plump, pelvis-jerking, cleavage-flashing temptress, she has metamorphosed into a sleek, accomplished actress. Gone are most of the inane mannerisms, pouts, wiggles and giggles." It further noted that her career prospects had begun to improve significantly, as leading filmmakers had started taking more notice of her and become more keen to cast her in their films.

Rekha went on to star opposite Bachchan in a number of films, most of which were hits. She also had an alleged off-screen relationship with him, which was widely reported on in the media, as well as sharply criticised, as he was a married man. This relationship ended in 1981, when they starred in Yash Chopra's drama Silsila. The film was the most scandalous of their films together; Rekha played Bachchan's love interest, while Bachchan's real-life wife, Jaya Bhaduri, played his wife. This was their last film together.

Critics noted Rekha for having worked hard to perfect her Hindi and acting, and media reporters often discussed how she had transformed herself from a "plump" duckling to a "swan" in the early 1970s. Rekha's credits to this transformation were yoga, a nutritious diet, and a regular, disciplined life. In 1983, her diet and yoga practice were published in a book called "Rekha's Mind and Body Temple".

In 1981, she starred in Umrao Jaan, a film adaptation of the Urdu novel Umrao Jaan Ada (1905), written by Mirza Hadi Ruswa. Rekha played the title role of a courtesan and poet from 19th century Lucknow. The film follows Umrao's life story right from her days as a young girl named Amiran when she is kidnapped and sold in a brothel. Rekha once confessed, "After reading the script, I had a strange feeling that I had Umrao in me." In preparation for the role, Rekha, who at the beginning of her career did not speak Hindi, took the task of learning the finer nuances of the Urdu language. Director Muzaffar Ali later noted that "Rekha has given more than my conception of the role." The response to her work was universally positive. Her portrayal is considered to be one of her career-best performances, and she was awarded the National Film Award for Best Actress for it. She played a courtesan with a heart of gold in several of her films; Muqaddar Ka Sikandar and Umrao Jaan were followed by a number of films which had her playing similar roles.

In that same year, Rekha starred in Ramesh Talwar's family drama Baseraa, which saw her playing a woman who marries her sister's husband, after the latter loses her mental balance. She appeared as Sadhna in the commercially successful Ek Hi Bhool (1981), opposite Jeetendra, playing the role of a betrayed wife who leaves her husband. In 1982, she received another Filmfare nomination for Jeevan Dhaara, in which she played a young unmarried woman who is the sole breadwinner of her extended family. In 1983, she took the supporting role of a lawyer in Mujhe Insaaf Chahiye, garnering another Filmfare nomination in the Supporting Actress category.

During this period, Rekha was willing to expand her range beyond what she was given in mainstream films. She started working in arthouse pictures with independent directors, mostly under Shashi Kapoor's production, in what was used to be referred to as parallel cinema, an Indian New Wave movement known for its serious content and neo-realism. Her venture into this particular genre started off with Umrao Jaan, and was followed by other such films as Shyam Benegal's award-winning drama, Kalyug (1981), Govind Nihalani's Vijeta (1982), Girish Karnad's Utsav (1984) and Gulzar's Ijaazat (1987), among others. Benegal's Kalyug is a modern-day adaptation of the