Isidor Straus was born into a Jewish family in Otterberg in the former Palatinate, then ruled by the Kingdom of Bavaria. He was the first of five children of Lazarus Straus (1809–1898) and his second wife and first cousin, Sara Straus (1823–1876). His siblings were Hermine (1846–1922), Nathan (1848–1931), Jakob Otto (1849–1851) and Oscar Solomon Straus (1850–1926). In 1854 he and his family immigrated to the United States, following his father, Lazarus, who immigrated two years before. They settled first in Columbus, Georgia, and then lived in Talbotton, Georgia, where their house still exists today. He was preparing to go to the United States Military Academy at West Point when the outbreak of the American Civil War prevented him from doing so. In 1861, he was elected an officer in a Confederate military unit but was not allowed to serve because of his youth; in 1863, he went to England to secure ships for blockade running.

In 1871, Isidor Straus married Rosalie Ida Blun (1849–1912). They were parents to seven children (one of whom died in infancy):

Isidor Straus worked at L. Straus & Sons, which became the glass and china department at Macy’s. In 1888, he and Nathan Straus became partners of Macy’s. In 1893 he and his brother bought a controlling interest in Wechsler & Straus, renamed Abraham & Straus. By 1896, Isidor and his brother Nathan had gained full ownership of R. H. Macy & Co.

He served as a U.S. Congressman from January 30, 1894, to March 3, 1895, as a Democratic representative of New York’s 15th congressional district. He won a special election in January 1894 to complete the term of Ashbel P. Fitch, who had resigned to become New York City Comptroller. Straus did not run for re-election in the general election of November 1894. Also, Straus was president of The Educational Alliance and a prominent worker in charitable and educational movements, very much interested in civil service reform and the general extension of education. He declined the office of Postmaster General which was offered him by U.S. President Grover Cleveland.

Traveling back from a winter in Europe, mostly spent at Cape Martin in southern France, Isidor and his wife were passengers on the RMS Titanic when, at about 11:40 p.m. on April 14, 1912, it hit an iceberg. Once it was clear the Titanic was sinking, Ida refused to leave Isidor and would not get into a lifeboat without him. According to friend and Titanic survivor Colonel Archibald Gracie IV, when he offered to ask an officer if Isidor could enter a lifeboat with Ida, Isidor refused to be made an exception; Ida is reported to have said, “I will not be separated from my husband. As we have lived, so will we die, together.” Ida gave her maid, Ellen Bird, her fur coat and insisted she get into lifeboat #8. Isidor and Ida were last seen on deck arm in arm. Eyewitnesses described the scene as a “most remarkable exhibition of love and devotion”. The ship sank at 2:20 am. Isidor’s body was recovered by the cable ship Mackay-Bennett and taken to Halifax, Nova Scotia, where it was identified before being shipped to New York. He was first buried in the Straus-Kohns Mausoleum at Beth-El Cemetery in Brooklyn, then moved to the Straus Mausoleum in Woodlawn Cemetery in the Bronx in 1928. Ida’s body was never found, so the family collected water from the wreck site and placed it in an urn in the mausoleum. Isidor and Ida are memorialized on a cenotaph outside the mausoleum with a quote from the Song of Solomon (8:7): “Many waters cannot quench love—neither can the floods drown it.”

The couple is portrayed in the 1953 film Titanic, the 1958 film A Night to Remember, and in the musical Titanic, in scenes that are faithful to the accounts described above. In the 1997 film Titanic, the Strauses are briefly depicted kissing and holding each other in their bed as their stateroom floods with water, during a sequence of emotional events while the ship’s string quartet plays the hymn “Nearer My God to Thee”. A deleted scene shows Isidor (played by Lew Palter) attempting to persuade Ida (played by Elsa Raven) to enter a lifeboat, which she refuses to do.