Karen MacKenzie (née Cooper; formerly Fairgate) is a fictional character in the CBS primetime soap opera Knots Landing. Karen is portrayed by actress Michele Lee, and has appeared on the show since its pilot episode, first broadcast on December 27, 1979. Knots Landing follows the trials of four middle-class families living on a suburban cul-de-sac known as Seaview Circle in California. Lee portrayed Karen for the entire run of Knots Landing, being the sole cast member to appear in every episode of its fourteen seasons. At the time, her appearances in all 344 episodes set a record for an actress on American primetime television. Karen's storylines focus on family troubles, business dealings, addiction, and kidnapping.

Series creator David Jacobs said "Karen is the tent pole. She says the things I want to say. She's the voice of the viewer." Entertainment Weekly also described Karen as being "efficient, kind, and understanding". During the course of her existence on the program, she was married to both Sid Fairgate (Don Murray) and second husband Mack MacKenzie (Kevin Dobson). Many other characters would try to undermine her relationship with Mack, such as his daughter Paige Matheson (Nicollette Sheridan), and former love interest Anne Matheson (Michelle Phillips), though Karen came to accept Paige as his daughter later on.

Due to her long-running tenure, television personality Joan Rivers commented that Lee was, in theory, the "First Lady of Knots Landing" during her guest appearance on The Late Show, which Rivers hosted at the time. The characters of the series often represented what was happening in society at the time, which Lee acknowledged by saying: "Karen wanted to be a Pollyanna and wasn't ashamed of that. Remember in our society, maybe people don't remember, but remember when we could go over to other people's houses and come in through an open back door? I remember when I was a little girl and my mother and father would have people over and they'd walk into an unlocked door in our house."

Prior to being cast in Knots Landing, Michele Lee had made a slew of film and television appearances. Lee holds the sole record for appearing in all 344 episodes of the dramatic series, setting a record at the time for a female actress in primetime television history. (S. Epatha Merkerson, who portrayed character Anita Van Buren on the crime drama Law & Order, surpassed Lee's record in 2008.) After the success of Dallas, David Jacobs' presented his initial idea again and created Knots Landing, with some alterations of his original script. In an interview, Jacobs explained: "Well, that's pretty good, but you know-and then he pulled out the pages that we'd left for them a few years ago on the show, or a year before on Knots, and he said, 'Is there any way we can make this a spin-off?' I just took one of the couples and made it, you know, Val and Gary who had already been created on the parent series and putting them into the mix, but when you have four couples and you change one, you sort of have to change the dynamic all the way around. However, once I wrote the script, remarkably little changed from the script and the pilot as you would see it."

Entertainment Weekly has said of Lee's character, "Her character, Karen MacKenzie, is efficient, kind, and understanding. Today, she's headed for big trouble, but Karen, onetime widow, single mom, addict, kidnappee, shooting victim, talk show hostess, and target of a psychotic fan, is resilient. Some on Knots say the show could not survive the loss of its moral mouthpiece." In 1991, the actress herself also commented, "Karen has gone through so much that it's hard to get her a [new] story line. Although she may be the only character who doesn't need a story line. She's a rock. She helps solve the problems. Certainly, after 12 years of playing Karen, you think, 'Oh, God, I wish I could play the town slut. But I have to save those roles for my hiatus."

Jacobs also said, "Karen, Michele Lee's character, was - made the speeches that I would have made about subjects, so she sort of was my footprint. . .but she was different. And also, I never had to - I never had a problem hearing Karen, you know. She and I spoke the same way." The character evolved significantly from the beginning of the series to the end. In the beginning, Karen was somewhat of a "bad girl" in order to lure over some fans of J.R. Ewing from Dallas. He noted:

"Well, Karen in the beginning was limited by her - well, we made Karen a little bit harsher in the first season than we otherwise would have because we were toying with the audience. And because it was a Dallas spin-off, the natural question was always, 'Well, where's your JR? Who's your JR?' And so, even though Michele Lee herself is a very likeable person, and even if she's being over the top she's a person of great enthusiasm, she's a person of great strength, in the pilot anyway, we were sort of pushing the possibility that she was gonna be roughly our equivalent. I always wanted to project the idea that we weren't Dallas, it was a different scale from Dallas, that whoever we had wasn't gonna be as successful as JR. But later on, the line "being married to a saint" was - Don Murray was so sweet, you know, and so rational all the time that, um, her enthusiasm, or the size of her enthusiasm, sometimes grew shrill and - I don't remember the context in which she said,'It's difficult being married to a saint" - but it's true, Sid had - you know, even the way he ran his business was totally moral. He was a totally moral kind of guy. Then later on, when Kevin makes the comment to her, it's really about her - um - if I recall, it's really about her correctness, you know, her dedication to her issues."

Though she was often a maternal figure, Karen was never able to become a grandmother on the serial. Lee said on her personal website, "Yes. I know it might sound like a big ego...far from it. It was a business option to prolong a career."