Harold Stirling Vanderbilt, born July 6, 1884 - died July 4, 1970, was a member of the prominent United States Vanderbilt family who was a railroad executive, a champion yachtsman and a champion bridge player.

Born in Oakdale, New York, the third child and second son of William Kissam Vanderbilt and Alva Erskine Smith, to family and friends he was known by the nickname "Mike." He was a brother to William Kissam Vanderbilt II and Consuelo Vanderbilt. Born to great wealth, he was raised in Vanderbilt mansions, traveled to Europe frequently, and sailed around the world on yachts owned by his father.

Educated by tutors and at private schools, Harold Vanderbilt attended Harvard Law School, graduating in 1910. He then joined the New York Central Railroad Company, the centerpiece of his family's vast railway empire of which his father was president. On his father's passing in 1920, thirty-six-year-old Harold Vanderbilt inherited a multi-million dollar fortune that included the Idle Hour summer estate at Oakdale on Long Island, New York plus equity in the following railway companies:

• Detroit Toledo & Milwaukee Railroad Co.
• Genesee Falls Railway Co.
• Kanawha & Michigan Railway Co.
• Kanawha & West Virginia Railroad Co.
• New Jersey Junction Railroad Co.
• New York Central Railroad Company
• New York Central & Hudson River Railroad Company
• New York & Harlem Rail Road Co.
• Pittsburgh & Lake Erie Rail Road Co.

Yachting was a major sport and pastime for the wealthy families. As a boy, Harold Vanderbilt spent part of his summers at his family's vacation mansions, the Idle Hour estate in Long Island, New York on the banks of the Connetquot River , and Marble House at Newport, Rhode Island. As an adult, he pursued his interest in yachting, winning six "King's Cups" and five "Astor Cups" at regattas between 1922 and 1938. In 1925, he built his own luxurious vacation home at Palm Beach, Florida that he called "El Solano." In 1930 he built a second Florida mansion, the same year that he achieved the pinnacle of Yacht racing success by winning the America's Cup. His victory put him on the cover of the September 15th issue of Time magazine. Held every three years, Harold Vanderbilt won the prestigious event three times in a row, taking it again in 1934 and 1937. His wife, Gertrude "Gertie" Lewis Conway became the first female to compete as a full-fledged team member in an America's Cup yacht race. They both were elected to the America's Cup Hall of Fame.

Vanderbilt was also a card game enthusiast who, in 1925, invented contract bridge. Three years later, he donated the Vanderbilt Trophy to go to the winners of the national team-of-four championship. In 1932 and again in 1940, he was part of a team that won his own trophy and he penned several books on the subject. In 1969, the World Bridge Federation made Vanderbilt its first honorary member. When a Bridge Hall Of Fame was inaugurated in 1964, Vanderbilt was one of the first of three persons elected. His trophy remains one of the most prized in the game.

In addition to sailing, Vanderbilt was a licensed pilot, acquiring a Sikorsky S-43 "Flying Boat" in 1938. But beyond leisure activities, Harold Vanderbilt had a keen interest in the success of Vanderbilt University in Nashville, Tennessee, founded in 1873 through the financial sponsorship of his great-grandfather, Cornelius Vanderbilt. A longtime member of the university's Board of Trust, he served as its president between 1955 and 1968. He helped guide the institution through a time in history when racial integration of the student body was a divisive and explosive issue. The university annually offers the "Harold Stirling Vanderbilt Scholarship" and on the grounds in front of Buttrick Hall, a lifelike statue was erected in his honor.

Following the death of his brother William, he became president of New York Central Railroad Company. Unfortunately, Harold Vanderbilt paid too little attention to the family's railway business and failed to adequately diversify as technology rapidly changed the world. He was the last of the Vanderbilts to head up the railroad, losing control of the company in 1954.

In 1963, Harold Vanderbilt assisted the Preservation Society of Newport County in acquiring the Marble House summer estate in Newport, Rhode Island sold by his mother more than thirty years earlier. Successful in their bid, the property was converted into a museum.

Harld Stirling Vanderbilt passed away in 1970. He and his wife are interred at Saint Mary's Cemetery in Portsmouth, Rhode Island, their graves marked with only a simple flat stone.