Isidore the Laborer, also known as Isidore the Farmer, was a devout Mozarab farmworker who lived in medieval Madrid. His piety toward the poor and animals led to his veneration as a Catholic patron saint of farmers and of Madrid, El Gobernador, Jalisco, La Ceiba, Honduras, and Tocoa, Honduras. Isidore was born in Madrid around 1070 or 1082 to poor, devout parents and worked as a hired hand on a farm. He shared his meals with the poor and was known for his miraculous deeds, including bringing back to life his master's deceased daughter and causing a fountain of fresh water to burst from the dry earth. Isidore's wife, Maria, always kept a pot of stew on the fireplace in their humble home to feed the hungry, and numerous miracles have been attributed to him. His feast day is celebrated on 15 May, and the number of miracles attributed to him has been counted as 438. Isidore died in 1130, and his body was discovered in an apparent state of incorruptibility in 1212. His relics were believed to possess curative powers, with King Philip III of Spain being cured of a deadly disease after touching them. Throughout history, members of the royal family sought curative powers from the saint.

Isidore Singer (10 November 1859 – 20 February 1939) was an American encyclopedist and editor of The Jewish Encyclopedia. Born in Weisskirchen, Moravia, he studied at the University of Vienna and the Humboldt University of Berlin, receiving his Ph.D. in 1884. Singer was an influential figure in promoting the rights of individuals, as evidenced by his founding of the American League for the Rights of Man. His career took him from Vienna to Paris, where he was active in advocating for Alfred Dreyfus, and eventually to New York City, where he realized his vision of the Jewish Encyclopedia. Singer's liberal religious views often sparked controversy, but his contributions to literature and his efforts to promote understanding among followers of different faiths left a lasting impact. He passed away in 1939 in New York City. Singer's publications include "Russia at the Bar of the American People: A Memoir of Kinship" (1904) and "The German Classics" (1913–1914), among others.

Sir Isidore Salmon CBE DL JP (10 February 1876 – 16 September 1941) was a prominent British businessman, conservative politician, and influential figure in the catering industry. He hailed from a family known for founding the successful Salmon & Gluckstein tobacconists, which later expanded into catering under Joseph Lyons. Salmon's notable career included serving as a Municipal Reform Party councillor for the London County Council and being elected as a Member of Parliament for the Harrow division of Middlesex. His contributions extended to promoting catering skills education, chairing the Westminster Technical School, and advocating for improved food standards in the British Army. Additionally, he played a significant role in Jewish charities and in persuading the Daily Mail to withdraw support for the British Union of Fascists. Beyond his professional accomplishments, Salmon was a devoted family man, married to Kate Abrahams, with whom he had two sons, Samuel Isidore Salmon and Julian Salmon. His legacy continues to be remembered for his multifaceted contributions to business, politics, and social causes.

Isidore De Loor (1881-1916), known as Isidore of Saint Joseph, was a devout Belgian religious figure of the Passionists. Despite battling cancer, he served selflessly as a janitor and cook at various convents. Born in East Flanders, Belgium, he displayed religious devotion from a young age and joined the Passionists in 1907. His strong will and charitable nature earned him admiration from his peers. Diagnosed with cancer, he endured the pain without complaint and continued to offer assistance during World War I. His health deteriorated, and he passed away in 1916. Isidore De Loor was beatified in 1984 after being recognized for his heroic virtue and life of service. His legacy continues to inspire and is upheld by the Passionist priest Giovanni Zubiani. His selfless dedication and unwavering faith have left a lasting impact, making him a revered figure in the Belgian religious community.

Isidore Springer (23 July 1912 in Antwerp, 27 December 1942 in Lyon, France) was a Belgian diamond dealer and communist who played a crucial role in the Red Orchestra organization during World War II. He worked closely with Soviet agents, serving as a recruiter and courier between Leopold Trepper and Anatoly Gurevich. Springer operated the 6th network of Trepper's espionage networks in France, gathering intelligence from US and Belgian diplomats. His aliases included Romeo, Verlaine, Walter van Vliet, Fred, and Sabor.Springer's personal life was intertwined with his espionage activities, as his wife, Flore Valaerts, also contributed to the network. Tragically, both were arrested and faced severe consequences. Isidore Springer was sent to Fresnes Prison and committed suicide, while Flore Valaerts was guillotined.Before his involvement in espionage, Springer fought against fascist forces in Spain and was an active member of the Communist Party of Belgium. His life came to a tragic end, but his contributions to the Red Orchestra and his role as a key figure in Soviet espionage during World War II are remembered.