Ygnacio Sepulveda (1842–1916) was one of the first two judges of the Superior Court in Los Angeles County, California, and a noted attorney there and in Mexico City, Mexico.
Ygnacio Sepulveda was born on July 1, 1842 in the Pueblo de Los Ángeles, Alta California, Mexico. He was the son of Jose Andres Sepulveda, grantee of Rancho San Joaquin in present day Orange County, and Francisca Avila. His grandfather was Francisco Sepulveda, the grantee of Rancho San Vicente in present day Los Angeles County. His early boyhood was spent in Los Angeles, but when older he was sent to prep schools in Boston, Massachusetts.
He was married on December 13, 1883, to Herlinda de la Guerra of Santa Barbara, California. He and his wife, who died in 1920, had two daughters, Conchita Sepulveda Chapman and Ora Sepulveda. He had two sisters, Mrs. Thomas D. Mott and Tranquilina Sepulveda.
Sepulveda was admitted to the California State Bar in 1860 or 1863 and, as a Democrat, he served one term in the California Legislature (1863–65). He was elected a county judge in 1863 or 1869 and a district judge in 1874 or 1875. He became one of the first two Superior Court judges for Los Angeles County in 1879, the other being Volney E. Howard. In 1872 he was a member of the first governing board for the Los Angeles Public Library system.
In December 1883 Sepulveda left Los Angeles and moved to Mexico City, where he spent thirty years practicing law and became the administrator of jurisprudence and legislation under the administration of President Porfirio Diaz of Mexico. In 1895 he was made the first secretary and chargé d'affaires of the United States in Mexico. While in that country, in 1905 he helped organize the Guadalupe Council of the Knights of Columbus.