Isidor Straus (February 6, 1845 – April 15, 1912) was a Bavarian-born American businessman, politician and co-owner of Macy's department store with his brother Nathan.

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.

[4] 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.

They were parents to seven children (one of whom died in infancy): Among his great-great-granddaughters are singer Mikaela Mullaney Straus, known by her stage name King Princess,[11] and Wendy Rush (née Weil), the widow of Stockton Rush who founded the deep sea tourism company OceanGate and lost his life on a dive in a submersible in 2023 to the wreck of the Titanic.

He won a special election in January 1894[13] to complete the term of Ashbel P. Fitch, who had resigned to become New York City Comptroller.

[14] When the newly formed Mutual Alliance Trust Company opened for business in New York on the Tuesday after June 29, 1902, there were 13 directors, including Emanuel Lehman, William Rockefeller, Cornelius Vanderbilt, and Straus.

[15] Traveling back from a winter in Europe, mostly spent at Cape Martin in southern France, Isidor and his wife were passengers on the Titanic when, at about 11:40 p.m. on April 14, 1912, it hit an iceberg.

In the 1997 film Titanic, the Strauses are briefly depicted (despite there being no evidence they returned to their cabin and despite the fact that Isidor's body was later recovered) kissing and holding each other on 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".