Today we honor the life and work of Sir Tony Hoare (1934–2026), one of the giants of computer science. His work shaped algorithms, programming languages, concurrency, and formal verification. In 1960, while a visiting student at Moscow State University working on a machine translation project, Hoare needed a way to sort the words of Russian sentences before looking them up in a Russian–English dictionary. His first idea was insertion sort, but this line of thinking led him to invent Quicksort — still one of the most widely used sorting algorithms in the world. In 1969 he introduced Hoare Logic in An Axiomatic Basis for Computer Programming, giving us the famous Hoare triple {P} C {Q} and launching the field of formal reasoning about programs. He also created Communicating Sequential Processes (CSP), a foundational model for concurrency and message-passing systems that influenced languages and systems for decades. Hoare also introduced null references in ALGOL W, which he later called his “billion-dollar mistake,” a candid reflection that pushed language designers toward safer type systems. For these and many other contributions he received the ACM Turing Award in 1980. Few researchers have shaped the intellectual foundations of our field so deeply. Thank you, Tony Hoare. May you rest in peace.