- X, Malcolm, (1925-1965), US Black Nationalist leader
- Xanothopoulos, Callistus, patriarch of Constantinople
- Xanthippe, wife of Socrates
- Xanthopoulos, Isidore, patriarch of Constantinople
- Xavier, Francis, (1506-1552), Spanish missionary
- Xenakis, Iannis, (1922-2001), Greek composer
- Xenocrates, (396 - 314 BC), philosopher
- Xenophanes, philosopher
- Xenophon, (431- c. 360 BC), Athenian knight, philosopher
- Xerxes I, (486- 465 BC), Persian king
- Xerxes II, (424 - 423 BC), Persian king.
- Xiang Yu, (232 - 202 BC), a powerful warlord
- Ximenes, Ettore, (1855-1919), Italian painter
- [[Fort?m鮥z|Xim鮥z, Fort?(d. 1533), early Spanish colonizer in Mexico
- Xiphilinus, George, patriarch of Constantinople
- Xiphilinus, John, (died 1078), patriarch of Constantinople
- Xuan Zang, (602-644), Buddhist monk
- Xuxa, singer
- Xu Zhi Mo, melancholic poet of early 20th century China
