Eastwood married Margaret Neville "Maggie" Johnson then working for an auto parts suppliers company) on December 19, 1953 in Pasadena. They had met six months earlier on a blind date in Los Angeles, although Eastwood subsequently had a serious relationship in Seattle that summer with a young woman who became pregnant with his child—an alleged daughter who was given up for adoption, per biographer Patrick McGilligan—before Johnson announced her engagement to him in October. The marriage would not prove altogether smooth. "He thought they were too young, not well enough established," remarked biographer Richard Schickel in the only authorized book ever written about Eastwood.

Eastwood has been conscious of his health and fitness since he was a teenager, and practices healthful eating habits. As a young man making a name for himself during the production of Rawhide, Eastwood would be featured in magazines and journals, which often documented his health-conscious lifestyle. In the August 1959 edition of TV Guide, for Example, Eastwood was photographed doing push-ups. He gave tips on fitness and nutrition, telling people to eat plenty of fruit and raw vegetables, to take vitamins, and to avoid sugar-loaded beverages, excessive alcohol, and overloading on carbohydrates.

A decade later, an ongoing affair Eastwood was involved in (said to have lasted 14 years) with Dancer and Rawhide stuntwoman Roxanne Tunis (who was also married yet separated) produced his earliest verified child, daughter Kimber Eastwood (born Kimber Tunis; June 17, 1964), whose existence was kept secret from the public until July 1989, when the National Enquirer revealed her identity. Biographer Marc Eliot wrote of Johnson, "It is difficult to say for sure that she actually knew about the baby, although it would have been nearly impossible for her not to. Everyone on the set knew ... and it is simply too difficult to keep a secret like that when the mother and the illegitimate child live in the same small town, especially when that small town is Hollywood." The source for the 1989 Enquirer article that originally broke the story claimed Johnson was aware of Kimber's existence at all times and even met Roxanne Tunis in person when making an unannounced visit to the set of Breezy in 1972. Actress Barbara Eden, a onetime Rawhide guest star and witness to the affair with Tunis, said of Eastwood's relationship with Johnson: "They conducted a somewhat open marriage."

Ria Brown, the biographer of competitive Swimmer Anita Lhoest, claims Lhoest terminated a pregnancy by Eastwood without consulting him at one point during their late 1950s to early 1960s affair. Restaurant critic Gael Greene admitted to an affair with Eastwood that began when she was assigned to interview him on the set of 1970's Two Mules for Sister Sara. A fling with French model Cathy Reghin around the same time was one of his few extramarital involvements to receive press coverage of any kind during the fact. According to McGilligan, Eastwood had many other affairs, including with co-stars Inger Stevens (Hang 'Em High), Jean Seberg (Paint Your Wagon) and Jo Ann Harris (The Beguiled), as well as actresses Jill Banner, Catherine Deneuve, and Susan St. James, columnist Bridget Byrne and singer Keely Smith while married to Johnson, who, after a trial separation and lingering bout of hepatitis during the mid-1960s, expressed Desire to reconcile and start a family. They had two children together: Kyle Eastwood (born May 19, 1968) and Alison Eastwood (born May 22, 1972).

On July 21, 1970, Eastwood's father died unexpectedly of a heart attack at the age of 64. The death, described by Fritz Manes as "the only bad thing that ever happened to him in his life", came as a shock to Eastwood, as his grandfather had lived to be 92. It had a profound impact on Eastwood's life; from then on he became more productive, working with a greater sense of urgency and with more speed and efficiency on set. Although Eastwood had always been a health and fitness enthusiast, he became more so after his father's death. He abstained from hard liquor, adopted a more rigorous health regime, and sought to stay fit. However, he still favored cold beer and opened a pub called the Hog's Breath Inn in Carmel-by-the-Sea in 1971. Eastwood eventually sold the pub and now owns the Mission Ranch Hotel and Restaurant, also located in Carmel-by-the-Sea.

In 1972, Eastwood met Actress (later director) Sondra Locke. The two began living together while filming The Outlaw Josey Wales in the autumn of 1975, by which time, according to Locke, "He had told me that there was no real relationship left between him and Maggie." Locke wrote in her autobiography, "Clint seemed astonished at his need for me, even admitting that he'd never been faithful to one woman — because he'd "never been in love before," he confided. He even made up a song about it: "She made me monogamous." That flattered and delighted me. I would never doubt his faithfulness and his love for me."

In 1975, Eastwood publicly proclaimed his participation in Transcendental Meditation when he appeared on The Merv Griffin Show with Maharishi Mahesh Yogi, the founder of Transcendental Meditation. He has meditated every morning for years. Eastwood is an experienced pilot, and sometimes flies his own helicopter to the studio to avoid traffic.

Eastwood and Locke went on to star in The Gauntlet, Every Which Way But Loose, Bronco Billy, Any Which Way You Can and Sudden Impact. According to former longtime associate Fritz Manes, as quoted by author McGilligan, Eastwood was devoted to her between 1976 and 1980 at the least, but discreetly kept up several "maintenance relationships" (such as with Tunis) during that period.

In 1978 Johnson filed for legal separation from Eastwood, but did not file for divorce until May 1984, a divorce which was finalized that November with Johnson receiving a straight cash payment reported to be between $25 and $30 million.

McGilligan claims Eastwood returned to his "habitual womanizing" in the early 1980s, becoming involved with story analyst Megan Rose, Actress Jamie Rose (who played a bit part in Tightrope), animal rights Activist Jane Brolin (who had intermittent liaisons with Eastwood between the early 1960s and late 1980s) and Jacelyn Reeves, a stewardess he met at the Hog's Breath Inn, among others. He was still living with Locke when he conceived two children with Reeves: a son Scott Eastwood (born Scott Reeves; March 21, 1986) and daughter Kathryn Eastwood (born Kathryn Reeves; February 2, 1988), whose birth certificates both said "Father declined." The affair with Reeves was not reported anywhere until an exposé article was published in the Star tabloid in 1990. It quoted Reeves as saying "Some family members tell me to file a paternity suit against Clint, but I don't want to." The children continued to be unacknowledged by mainstream news sources for more than a decade thereafter.

Eastwood's relationship with Locke (at the time unaware of his infidelities) ended acrimoniously in April 1989, and the post-breakup litigation dragged on for years. Locke filed a palimony lawsuit against him after he changed the locks on their home and moved her possessions into storage when she was at work filming her second directorial feature, Impulse. In court, Eastwood downplayed the intensity of their relationship. He described Locke as a "roommate" before quickly redescribing her as a "part-time roommate." Locke's estranged brother told The Tennessean that Eastwood still truly loved her, but could no longer take her "addiction" to husband Gordon Anderson. Anticipating that Eastwood was going to misrepresent the marriage, Locke asked Anderson to surrender all claims on any of her assets that as her legal spouse he was entitled to. "In an extraordinary gesture of love and faith in me, Gordon signed away everything without hesitation." During the trial, an investigative Journalist contacted Locke and informed her of Eastwood's other family. "I spoke with the nurse in the delivery room, and she confirmed that they are Clint's children. I'll send copies of the birth certificates to you and a photo of Jacelyn, if you want them," Locke quotes the informant. "My mind was still searching to get all his actions lined up. For at least the last four years of our relationship, Clint had been living this double life, going between me and this other woman, and having children with her. Two babies had been born during the last three years of our relationship, and they weren't mine." As the case went on, Locke developed breast cancer and said the treatments sapped her will to fight. She dropped her suit in November 1990 in exchange for a settlement package which included a lump sum plus monthly support payments from Eastwood and a $1.5 million directing deal at Warner Bros., but sued him again for fraud in 1995 when she became convinced the deal with Warner was a sham, finally settling out of court in September 1996. Since then, Locke has made discrediting comments about Eastwood.

In 1990, Actress Frances Fisher, whom Eastwood had met on the set of Pink Cadillac in late 1988, moved in with him. Fisher said of dating Eastwood, "I simply felt that this was it, the big one. I had no idea that every woman he meets probably feels as I did." They co-starred in Unforgiven, and had a daughter, Francesca Eastwood (born Francesca Fisher-Eastwood; August 7, 1993). The birth of Francesca marked the first time Eastwood was present for one of his children being born. Eastwood and Fisher ended their relationship in early 1995, after which Fisher said it took two years to complete what she called the grieving process for her shattered dreams.

Before Fisher had moved out of Eastwood's home, he was said to already be dating Dina Ruiz, a television news anchor 35 years his junior whom he had first met when she interviewed him in April 1993. They married on March 31, 1996, when Eastwood surprised her with a private ceremony at a home on the Shadow Creek Golf Course in Las Vegas. The marriage was noted for the fact that it was only Eastwood's second legal union in spite of his many long-term romances over the decades. Eastwood said of his bride, "I'm proud to make this lady my wife. She's the one I've been waiting for." Ruiz commented, "The fact that I'm only the second woman he has married really touches me." The couple has one daughter, Morgan Eastwood (born December 12, 1996). Ruiz made cameos in two of Eastwood's films, Blood Work and True Crime (in which Fisher even appeared). In the summer of 2012, Dina, Morgan and Francesca starred with the band Overtone in a reality show for the E! network titled Mrs. Eastwood & Company, on which Clint appeared only occasionally.

In August 2013, Dina Eastwood announced that she and her husband had been living separately for an undisclosed length of time. On October 23, 2013, Dina filed for divorce after she withdrew her request for legal separation, citing irreconcilable differences. She asked for full custody of their 16-year-old daughter, Morgan, as well as spousal support. The divorce was finalized on December 22, 2014.

Since his split from Ruiz, Eastwood has been linked publicly with Photographer Erica Tomlinson-Fisher (no relation to Frances), 41 years his junior, and restaurant hostess Christina Sandera, 33 years his junior. He and Sandera went public with their relationship at the 87th Academy Awards in February 2015.