Count László Széchenyi de Sárvár-Felsővidék (18 February 1879 – 5 July 1938) was an Austro Hungarian military officer, Imperial Chamberlain, diplomat and venture capitalist. His great-uncle was Count István Széchenyi. László Széchenyi married Gladys Vanderbilt, the youngest daughter of Alice Claypoole Gwynne and Cornelius Vanderbilt II.^[1]

The Count was born Széchenyi László Jenő Mária Henrik Simon on February 18, 1879 in Horpács, then a part of Austria-Hungary, a dual monarchy established in 1867. He was a son of Count Imre Széchenyi de Sárvár-felsővidék, the former Austrian Minister at the Court of Berlin and his wife, Countess Alexandra Sztaray-Szirmay et Nagy-Mihály (1843–1914).^[2] The Széchényi family were one of the oldest and wealthiest in the Austro-Hungarian Empire.^[3]

He was the youngest of four brothers, including: Count Dionys, who was Minister of the Austrian Embassy at Paris (he married Comtesse Marie de Caraman et Chimay), Peter Széchenyi, and István Széchenyi. All of the brothers were Reserve Lieutenants in the Imperial Hussars as well as Chamberlains at the Court.^[4]

His father owned thousands of acres divided into scores of farms and forest preserves on which the Széchenyis grew wheat, Turkish pepper, tobacco, hemp, and grapes.^[1]

Count Széchenyi was the inventor of the submarine wireless telegraphy, for sending and receiving sound-wave vibrations underwater. The machine was successfully tested with then U.S. Secretary of the Navy George von Lengerke Meyer, in Newport, Rhode Island. Széchenyi, along with David C. Watts, formed the Submarine Wireless Company to produce it.^[2]

By 1908, Count László Széchenyi de Sárvár-felsővidék was the most prominent member of his family, which was quite numerous. He possessed two great estates in Hungary, Oermezo Castle, which is about three hundred years old and 4,000 acres, in the County of Templen, and Lagoshara Pusbla, a Summer place of about 4,300 acres, in the County of Somogy. The Count also owned a one-story, ten room house at 14 Eotvoss-street in Budapest.^[5][6][7]

Shortly before the War, Count László Széchenyi de Sárvár-felsővidék tried to become a financial leader in Hungary but failed. He is said to have lost $4,000,000 which is supposed to have come largely from his wife. He was a member of the 'Magnates Group' which speculated in mines, railroads and other enterprises. They failed to calculate the impact of the World War, and suffered a complete smash as a result of the fall in value of their shares.^[5]

Count László was twenty-eight years old when he met Gladys Vanderbilt (1886–1965), the seventh and youngest child of Alice Claypoole Gwynne and Cornelius Vanderbilt II, the president and chairman of the New York Central Railroad. Gladys grew up in the family home on Fifth Avenue in New York City, and their summer "cottage," The Breakers in Newport, Rhode Island.^[10] They married on January 27, 1908, at her family home in New York City, after their meeting in Berlin near her twenty-first birthday in 1907.^[11][12] Their early married life was spent in Hungary raising their five children.^[13] Together, Count László Széchenyi and Gladys Moore Vanderbilt were the parents of five daughters:

• Countess Cornelia "Gilia" Széchényi (1908–1958),^[14] who married Eugene Bowie Roberts (1898–1983), an heir of the Roberts family of Bowie, Maryland, a Colonial family of Maryland.^[15]
• Countess Alice "Ai" Széchényi (1911–1974),^[16][17] who married Hungarian Count Béla Hadik (1905–1971), a son of Count János Hadik, who was briefly the Prime Minister of the Kingdom of Hungary.^[18]
• Countess Gladys Széchényi (1913–1978),^[19] who married the English Christopher Finch-Hatton, 15th Earl of Winchilsea (1911–1950). They divorced in 1945,^[20] and in 1954, she married American banker Arthur Talbot Peterson (1905–1962).^[21][22]
• Countess Sylvia Anita Gabriel Denise Irene Marie "Syvie" Széchényi (1918–1998), who married Hungarian Count Antal Szapáry von Muraszombath Széchysziget und Szapar (1905–1972).^[23]
• Countess Ferdinandine "Bubby" Széchényi (1923–2016), who married the Austrian Count Alexander von und zu Eltz genannt Faust von Stromberg (1911–1977).

Count László Széchenyi died in Budapest on 5 July 1938.^[9] His widow died on 29 January 1965 in Washington, D.C.^[24]