Her daughter, Kris Jenner, announced the heartbreaking news on social media on Thursday, paying tribute to the woman she described as the foundation of their close-knit family.
"Today, we said goodbye to my beautiful Mommy MJ," Kris Jenner wrote.
No cause of death was immediately disclosed.
MJ Campbell, who was born in 1934, became a familiar face to millions of viewers through the family's reality television shows, beginning with Keeping Up with the Kardashians, which premiered in 2007, and later The Kardashians. Over the years, she won over fans with her warmth, humour, candid advice and unwavering devotion to her family.
In her emotional tribute, Kris reflected on the values her mother instilled in generations of the Kardashian-Jenner family.
"She taught us that family is everything. She showed us how to love unconditionally and how to find joy in the little moments. She showed me how to face life's challenges with resilience and faith," she wrote.
MJ was the mother of Kris Jenner and Karen Houghton. The family had already endured tragedy in March 2024 when Karen died from cardiac arrest at the age of 65.
As grandmother to Kim, Kourtney and Khloé Kardashian, as well as Kendall and Kylie Jenner, MJ remained a constant presence in the family's lives and television journey. She frequently appeared alongside her daughter and grandchildren, often offering heartfelt advice while playfully teasing them about their glamorous lifestyles.
Her resilience also inspired many, as she openly spoke about surviving cancer twice, earning admiration from both her family and viewers.
The family had celebrated MJ's 90th birthday on an episode of The Kardashians, hosting a lavish floral-themed party at a hotel in San Diego, California. During the celebration, she reflected on what mattered most in her life.
"How wonderful life is when you're in my world... that's all of you," MJ said, adding that her greatest accomplishment was raising her two daughters.
The episode also captured an emotional moment when Kris Jenner broke down while contemplating the possibility of one day losing her mother.
"My best friend and I couldn't live without you," Kris told her, to which MJ reassuringly replied that she was not going anywhere and that they would simply have to wait for the next birthday celebration.
The family later honoured her 91st birthday with an intimate garden-themed gathering, continuing a tradition of celebrating the woman they often described as the heart of the family.
Following news of her passing, tributes poured in from family members, including Kim Kardashian, who remembered her grandmother as one of the most influential people in her life.
"My best friend, my gossip buddy, my forever twin," Kim wrote.
She added:
"You taught all of us the importance of family, and those values are something we'll carry with us forever!!!!! You were the woman who showed me what it meant to be a hardworking businesswoman."
Kim also revealed that MJ gave her her first job at a retail store in San Diego, where she learned lessons about discipline, confidence and a strong work ethic—qualities she says helped shape her entrepreneurial journey.
Kris Jenner also reflected on the lasting legacy her mother leaves behind.
"When I look at my kids and my grandkids, I will forever see pieces of you in all of us. There is not a part of me that isn't shaped by you. And if I have done anything right in this world, it's because I spent my life trying to live in a way that would make you proud."
MJ Campbell's legacy lives on through four generations of the Kardashian-Jenner family, whose global business empire and enduring popularity were built on the family values she championed throughout her life. Her warmth, resilience and unwavering devotion to family remain qualities that those closest to her say they will carry forward for generations.