Sixten is an Old Norse boy's name meaning "victory stone," composed of the elements sigr and steinn. A longer form was Siegstein. This name was #39 for boys in Sweden in 2016. Famous namesakes include Swedish lieutenant Sixten Sparre born in 1854, Swedish conductor Sixten Ehrling, inventor of pointcytology Sixten Franzen, Danish artist Sixten Kai Nielsen, Estonian orienteer Sixten Sild, and many athletes, such as Swedish cross-country skier Sixten Jernberg, who won 15 Olympic medals. Sixten can also be found as a surname, as is the case for composer Fredrik Sixten and priest Sven Sixten. The form Sixtens appears in the Dictionary of Medieval Names from European Sources (DMNES), dating to 1377.
The unrelated name Sixtus, meaning "sixth born" in Latin, was the name of five popes, two of whom became a saint. For the first (oldest) three, the spelling used was Xystus, dating to the 2nd century. As Xystus it may have meant "scraped, polished" in Greek, and "sixth" came about when Pope Sixtus I became the sixth pope after Saint Peter, possibly taking the name after Latin sextus. In Italy the name Sixtus dates to at least 1527. Sixtus of Tannburg was a Bishop, Sixtus of Sienna was a theologian, and Edmund Sixtus Muskie was 58th U.S. Secretary of State.
Neither name has been used more than four times in the U.S. in any given year.