Judi Ann Stish Ross Nathan Giuliani (born December 16, 1954) is an American registered nurse, former medical sales executive, charity fundraiser, and ex-wife of former New York City Mayor Rudy Giuliani. She was a managing director of philanthropic consulting firm Changing Our World and a founding board member of the Twin Towers Fund.

Judi Ann Stish was born and raised in Hazleton, Pennsylvania, a town known for its coal mining history. Her family is Roman Catholic of Italian descent on her father's side and Polish descent on her mother's side. The surname Stish was previously modified from Sticia. Her father, Donald Stish Sr., was a circulation manager for The Philadelphia Inquirer, and her mother, Joan Ann (Ososki), is a homemaker. She had an older brother, Donald Jr., who died in 2004, and has a younger sister, Cyndy. As of 2007, her parents still resided in the same home where she grew up in Hazleton.

Stish graduated from Hazleton High School in 1972, where she participated in the Future Nurses Association, the Literary Society, the tennis and ski clubs, and the Diggers Club, a volunteer service organization. Interested in both the human and scientific aspects of the field, she attended a two-year nursing program, affiliated with Pennsylvania State University, at St. Luke's Hospital in Bethlehem, Pennsylvania, and graduated with a registered nurse diploma on September 1, 1974. She credits her decision to become a registered nurse as "one of the most practical, wonderful ones I ever made…because, aside from the science, you learn crisis management, decision making, prioritizing…"

After graduation, Stish worked for a few months as a nurse at Sacred Heart Hospital in Allentown, Pennsylvania. On December 8, 1974, she and Jeffrey Ross, a medical supply salesman, eloped to Las Vegas and were married at the Chapel of the Bells. The couple soon relocated to Charlotte, North Carolina, where they both took jobs with U.S. Surgical Corporation in 1975 selling medical supplies in the Southeast; Judi Ross specialized in showing doctors in operating rooms a new surgical stapling method. She and Ross separated amicably after four years, and their marriage ended in divorce which was finalized on November 14, 1979. The couple had no children.

On November 19, 1979, Judi Stish Ross married wallpaper salesman Bruce Nathan, whom she had met during her separation from her first husband. Judi Nathan stopped working around that time; the couple lived in Charlotte for two years, then moved to Atlanta, Georgia. The Nathans adopted a daughter, Whitney, in March 1985. The family moved to Manhattan in 1987 and Pacific Palisades in Los Angeles in 1991. During these years, she briefly worked for DynaMed Surgical in California. She also converted from Roman Catholicism to Presbyterianism.

The Nathans' marriage fell apart during the early 1990s and led to a contested divorce case and custody battle, which included accusations of abuse from both parties. The Nathans' divorce was finalized in 1992 and she won primary custody of their child. Nathan, who came to prefer the name "Judith" around this time, moved back to New York in March 1992. Now a single mother, she worked part-time in a dentist's office and attended New York University computer and business classes at night and on weekends. Nathan received a New York nursing license and began working in 1993 as a pharmaceutical sales representative with the hospital sales division of Bristol-Myers Squibb, selling surgical supplies, anti-depressants, and antibiotics in the tough Bedford-Stuyvesant neighborhood of Brooklyn; one of her specialties was infectious diseases. Around this time Judith became romantically involved with Woodhull Hospital clinical psychologist Manos Zacharioudakis; she and her daughter lived with him for four years, until early 1999. By 1997, she became one of Bristol-Myers' top sales managers, managing a 12-person sales team.

Judith Nathan met Mayor Giuliani in May 1999 at Club Macanudo, an Upper East Side cigar bar; they have said they were introduced by a doctor who is a mutual friend. Giuliani took the initiative in forming an ongoing relationship. The mayor was still married to and living with his second wife, Donna Hanover, although they had been publicly distant since 1996, and Nathan was still living with Zacharioudakis although the couple had separated a few months earlier. For most of a year, the relationship was kept secret, and in early 2000 Giuliani arranged for New York Police Department security and chauffeuring for her. By March 2000, Giuliani and Nathan were appearing together at public events; in May 2000, Giuliani publicly acknowledged her as his "very good friend" and, amidst a flurry of press scrutiny about Nathan, announced he was separating from Hanover. Nathan endeared herself to the mayor's powerful inner circle of friends and advisers. Later in 2000, Giuliani credited Nathan's nursing background in helping him through his treatment for prostate cancer. Nathan aggressively researched treatment options and Giuliani was quoted as saying, "I felt so fortunate to have not only someone who loved me and cared about me, but also someone who was an expert with an enormous amount of knowledge of medicine and science — she was the single biggest support that I had."

Judith and Rudy Giuliani became engaged in Paris in November 2002 and married on May 24, 2003. The wedding was held at Gracie Mansion and was one of only two performed by Mayor Michael Bloomberg. The reception for 400 guests included figures from the political, entertainment, and fashion worlds. The couple had a $5 million apartment off Madison Avenue on the Upper East Side in Manhattan and a $4 million summer home in The Hamptons.